1. Physics (Level 2)
   1. Physicist
   2. Physics education
2. Outline of physics
3. Physical property
4. Physical quantity
5. Energy (Level 2)
   1. Conservation of energy (Level 4)
   2. Energy density
6. Homogeneity (physics)
7. Matter (Level 3)
   1. Exotic matter
   2. Physical object
8. Vacuum (Level 3)
9. Fundamental interaction
   1. Gravity (Level 3)
   2. Electromagnetism (Level 3)
   3. Strong interaction (Level 3)
   4. Weak interaction (Level 3)
   5. Fifth force
10. Spacetime (Level 4)
    1. Curved spacetime
    2. Space (Level 3)
       1. Action at a distance
       2. Principle of locality
    3. Time (Level 2)
       1. Arrow of time
       2. Time in physics
11. Mass–energy equivalence (Level 4)
12. Conservation law
13. Hysteresis
14. Transport phenomena
15. Radiation (Level 4)
    1. Ionizing radiation (Level 4)
    2. Background radiation
16. Scalar (physics)
17. Field (physics) (Level 4)
    1. Classical field theory
       1. Mean-field theory
       2. Renormalization
    2. Flux (Level 4)
18. Gauge theory (Level 4)
    1. Introduction to gauge theory
19. Symmetry (physics) (Level 4)
20. Instability
    1. Metastability
21. Classical physics
22. Modern physics
23. Naïve physics
24. Theoretical physics (Level 4)
25. Experimental physics
26. Computational physics
27. Atmospheric physics
28. Biophysics
29. Chemical physics
30. Polymer physics
31. Mathematical physics
32. List of unsolved problems in physics
33. Scale invariance
34. Classical limit
35. Macroscopic scale

1. Physical constant
2. Bohr magneton
3. Bohr radius
4. Boltzmann constant
5. Electron magnetic moment
6. Nucleon magnetic moment
7. Elementary charge
8. Fine-structure constant
9. Gravitational constant
10. Impedance of free space
11. Magnetic flux quantum
12. Planck constant
13. Speed of light (Level 3)
    1. Foucault's measurements of the speed of light
14. Vacuum permeability
15. Vacuum permittivity

This section contains 39 articles.

1. Atom (Level 2)
2. Atomic physics (Level 4)
3. Atomic orbital (Level 4)
4. Binding energy (Level 4)
5. Plum pudding model
6. Rutherford model
7. Bohr model (Level 4)
   1. Franck–Hertz experiment
8. Electron configuration (Level 4)
9. Electron shell (Level 4)
10. Exotic atom
    1. Onium
       1. Positronium
11. Ion (Level 4)
    1. Oxonium ion
12. Energy level (Level 4)
    1. Fine structure
    2. Hyperfine structure
    3. Spin–orbit interaction
    4. Degenerate energy levels
13. Rutherford scattering experiments (Level 4)
14. Principal quantum number
15. Azimuthal quantum number
16. Magnetic quantum number
17. Spin quantum number
18. Spectral line
    1. Stark effect
    2. Zeeman effect
    3. Stimulated emission
    4. Spontaneous emission
    5. Hydrogen spectral series
       1. Rydberg constant
       2. Rydberg formula
       3. Hydrogen-alpha
    6. Hydrogen line
    7. Einstein coefficients
    8. Optical pumping
19. Spherical harmonics
20. Density functional theory

This section contains 9 articles.

1. Molecular physics
2. Molecular orbital (Level 4)
   1. Molecular orbital theory (Level 4)
3. Rigid rotor
4. Molecular dynamics
5. Cross section (physics)
6. Emission spectrum
7. Rotational–vibrational spectroscopy
   1. Rotational spectroscopy

This section contains 39 articles.

1. Color (Level 3)
2. Blacklight
3. CIE 1931 color space
4. CIELAB color space
5. CIELUV
6. CMYK color model (Level 4)
7. Color theory (Level 4)
   1. Primary color (Level 4)
   2. Secondary color
8. Color model
9. Color space
10. Gamut
11. Gloss (optics) (Level 4)
12. HCL color space
13. HSL and HSV
14. HWB color model
15. ISCC–NBS system
16. Munsell color system
17. RGB color model (Level 4)
    1. RGB color spaces
       1. Adobe RGB color space
       2. DCI-P3
       3. eciRGB
       4. ProPhoto RGB color space
       5. Rec. 601
       6. Rec. 709
       7. Rec. 2020
       8. Rec. 2100
       9. scRGB
       10. sRGB
       11. Wide-gamut RGB color space
18. RGBA color model
19. RYB color model
20. Impossible color
21. Chromaticity
    1. Line of purples
22. Hue
23. Tint, shade and tone
24. Web colors

This section contains 47 articles.

1. Amber (color)
2. Azure (color)
3. Beige
4. Black (Level 4)
5. Blue (Level 4)
   1. Egyptian blue
   2. Navy blue
   3. Sky blue
   4. Ultramarine
6. Brown (Level 4)
7. Burgundy (color)
8. Celadon
9. Cerulean
10. Chartreuse (color)
11. Bronze (color)
12. Cyan
13. Fuchsia (color)
14. Gold (color)
15. Green (Level 4)
    1. Lime (color)
16. Grey (Level 4)
17. Indigo
18. Lavender (color)
19. Magenta
20. Mauve
21. Olive (color)
22. Orange (colour) (Level 4)
23. Pink (Level 4)
24. Purple (Level 4)
    1. Tyrian purple
25. Red (Level 4)
    1. Crimson
    2. Maroon
    3. Scarlet (color)
26. Rose (color)
27. Ruby (color)
28. Saffron (color)
29. Silver (color)
30. Spring green
31. Tan (color)
32. Teal
33. Turquoise (color)
34. Vermilion
35. Violet (color)
36. Viridian
37. White (Level 4)
38. Yellow (Level 4)

This section contains 17 articles.

1. Condensed matter physics (Level 4)
2. Solid-state physics (Level 4)
3. Mesoscopic physics
4. Einstein solid
5. Electronic band structure
   1. Band gap
   2. Fermi level
   3. Valence and conduction bands
6. Free electron model
7. Hubbard model
   1. Mott insulator
8. Soft matter
9. Bonding in solids
10. Rock magnetism
11. Bloch's theorem
12. Plasmon
13. Polaron

This section contains 32 articles.

1. Crystallography (Level 4)
2. Crystal (Level 4)
3. Crystallization (Level 4)
   1. Crystal growth
   2. Grain growth
4. Crystal structure
   1. Crystal system
      1. Triclinic crystal system
      2. Monoclinic crystal system
      3. Orthorhombic crystal system
      4. Tetragonal crystal system
      5. Hexagonal crystal family
      6. Cubic crystal system
   2. Perovskite (structure)
   3. Unit cell
      1. Bravais lattice
   4. Reciprocal lattice
      1. Brillouin zone
      2. Fermi surface
5. Crystal optics
6. Crystallographic defect
   1. Grain boundary
   2. Dislocation
   3. Misorientation
   4. Vacancy defect
7. Crystal twinning
8. Miller index
9. Atomic packing factor
10. Coordination number
11. Crystal polymorphism
12. X-ray crystallography
13. Crystal engineering

This section contains 19 articles.

1. State of matter (Level 3)
2. Solid (Level 4)
   1. Amorphous solid (Level 4)
3. Liquid (Level 4)
4. Gas (Level 4)
   1. Vapor (Level 4)
5. Plasma (physics) (Level 4)
   1. Vlasov equation
6. Degenerate matter (Level 4)
   1. Bose gas
   2. Fermi gas
7. Bose–Einstein condensate (Level 4)
8. Superfluidity
9. Supercritical fluid
10. Supersolid
11. Liquid crystal
12. Quasiparticle
    1. Electron hole
    2. Phonon

This section contains 25 articles.

1. Phase transition (Level 4)
2. Phase (matter) (Level 4)
3. Phase diagram (Level 4)
4. Boiling (Level 4)
   1. Boiling point
   2. Superheating
5. Melting (Level 4)
   1. Melting point
6. Freezing (Level 4)
7. Evaporation (Level 4)
8. Condensation (Level 4)
   1. Superheated steam
9. Vaporization
10. Ionization (Level 4)
11. Plasma recombination
12. Sublimation (phase transition)
13. Deposition (phase transition)
14. Critical point (thermodynamics) (Level 4)
    1. Self-organized criticality
15. Triple point (Level 4)
16. Miscibility
17. Metallization pressure
    1. Metallic hydrogen
18. Curie temperature
19. Phase rule

This section contains 14 articles.

1. Classical electromagnetism
2. Electricity (Level 2)
3. Magnetism (Level 3)
   1. Magnet (Level 4)
      1. Electromagnet (Level 4)
4. Dipole (Level 4)
5. Metamaterial (Level 4)
   1. Negative-index metamaterial
   2. Photonic metamaterial
   3. Tunable metamaterial
   4. Nonlinear metamaterial
6. Oil drop experiment (Level 4)
7. Photoelectric effect (Level 4)
8. Bubble chamber

This section contains 19 articles.

1. Electrostatics (Level 4)
   1. Static electricity
2. Coulomb's law (Level 4)
3. Electric charge (Level 4)
   1. Charge density
4. Electric field (Level 4)
   1. Electric displacement field
   2. Electric-field screening
      1. Debye length
5. Electric potential (Level 4)
   1. Voltage
6. Electric potential energy
7. Electric flux
8. Electric dipole moment
9. Polarization density
10. Dielectric (Level 4)
11. Electric susceptibility
12. Electrostatic induction
13. Permittivity

This section contains 20 articles.

1. Magnetostatics (Level 4)
2. Magnetic field (Level 4)
3. Magnetic flux
4. Biot–Savart law
5. Magnetic dipole
6. Magnetic moment
7. Magnetization
   1. Antiferromagnetism
   2. Diamagnetism
   3. Ferrimagnetism
   4. Ferromagnetism (Level 4)
      1. Ising model
      2. Potts model
   5. Paramagnetism
   6. Spontaneous magnetization
8. Magnetic susceptibility
9. Permeability (electromagnetism)
10. Magnetic monopole
11. Magnetohydrodynamics
12. Ampère's force law

This section contains 26 articles.

1. Maxwell's equations (Level 4)
   1. Gauss's law
   2. Gauss's law for magnetism
   3. Ampère's circuital law
   4. Faraday's law of induction
2. Lorentz force (Level 4)
3. Electromagnetic field (Level 4)
4. Electromagnetic four-potential
   1. Lorenz gauge condition
5. Electric current (Level 4)
   1. Alternating current (Level 4)
   2. Direct current (Level 4)
   3. Current density
6. Displacement current
7. Electric power
   1. AC power
8. Electromagnetic induction (Level 4)
9. Electromotive force (Level 4)
10. Eddy current (Level 4)
11. Hall effect
    1. Quantum Hall effect
12. Electrical resistivity and conductivity
13. Retarded time
14. Lenz's law
15. Poynting's theorem
16. Right-hand rule

This section contains 38 articles.

1. Electromagnetic radiation (Level 3)
   1. Electromagnetic wave equation
2. Electromagnetic spectrum (Level 4)
   1. Radio wave (Level 4)
   2. Microwave (Level 4)
   3. Terahertz radiation
   4. Infrared (Level 4)
   5. Light (Level 3)
      1. Visible spectrum (Level 4)
   6. Ultraviolet (Level 4)
   7. X-ray (Level 4)
   8. Gamma ray (Level 4)
3. Poynting vector
4. Evanescent field
5. Transverse mode
6. Waveguide (radio frequency)
7. Larmor formula
8. Bremsstrahlung (Level 4)
9. Cyclotron radiation
10. Synchrotron radiation
11. Compton scattering
12. Radiative transfer
13. Faraday effect
14. Absorption (electromagnetic radiation)
    1. Absorption band
15. Near and far field
16. Radiant flux
17. Irradiance
18. Point source
19. Radiance
20. Radiometry
21. Spectral density
22. Luminescence
    1. Fluorescence (Level 4)
    2. Phosphorescence
    3. Scintillation (physics)
       1. Scintillator
23. Thermal radiation

This section contains 24 articles.

1. Electrical network (Level 4)
2. Electrical impedance (Level 4)
3. Electrical reactance
4. Electrical resistance and conductance (Level 4)
   1. Joule heating
   2. Ohm's law (Level 4)
5. Electrical conductor
   1. Electrode
6. Insulator (electricity)
7. Semiconductor (Level 4)
   1. Depletion region
   2. Metal–semiconductor junction
   3. Ohmic contact
8. Superconductivity (Level 4)
   1. Cooper pair
   2. High-temperature superconductivity
   3. Josephson effect
   4. Type-I superconductor
   5. Type-II superconductor
9. Capacitance (Level 4)
10. Gain (electronics) (Level 4)
11. Ground (electricity)
12. Inductance (Level 4)
13. Kirchhoff's circuit laws (Level 4)

This section contains 25 articles.

1. Mechanics (Level 4)
   1. Ballistics (Level 4)
   2. Continuum mechanics (Level 4)
   3. Flight (Level 4)
   4. Kinematics (Level 4)
      1. Chasles' theorem (kinematics)
      2. Screw axis
   5. Mechanical advantage
   6. Relativistic mechanics (Level 4)
   7. Statics (Level 4)
2. Oscillation (Level 4)
   1. Harmonic oscillator (Level 4)
      1. Simple harmonic motion (Level 4)
   2. Normal mode
3. Collision
   1. Elastic collision
   2. Inelastic collision
4. Degrees of freedom (mechanics)
5. Free particle
6. Point particle
7. Virial theorem
8. Shock (mechanics)
9. Mechanical equilibrium
10. Displacement (geometry)
11. Test particle

This section contains 98 articles.

1. Quantum mechanics (Level 3)
   1. Introduction to quantum mechanics
   2. Quantum
2. AdS/CFT correspondence
3. Born rule
4. Bra–ket notation
5. Correspondence principle
   1. Ehrenfest theorem
6. Dirac equation
   1. Pauli equation
   2. Pauli matrices
7. Expectation value (quantum mechanics)
8. Gyromagnetic ratio
   1. g-factor (physics)
9. Interpretations of quantum mechanics
   1. Copenhagen interpretation
   2. De Broglie–Bohm theory
      1. Quantum potential
   3. Many-worlds interpretation
   4. Schwinger's quantum action principle
10. Hidden-variable theory
11. Mathematical formulation of quantum mechanics
12. Matrix mechanics
    1. BKS theory
13. Measurement in quantum mechanics
    1. Measurement problem
14. Observable
    1. Invariant (physics)
    2. Quantum contextuality
    3. Schrödinger's cat
15. Operator (physics)
    1. Angular momentum operator
    2. Hamiltonian (quantum mechanics)
       1. Unitary transformation (quantum mechanics)
    3. Momentum operator
    4. Position operator
    5. Rotation operator (quantum mechanics)
16. Parity (physics)
    1. Wu experiment
17. Particle in a box
    1. Finite potential well
       1. Delta potential
18. Path integral formulation
19. Pauli exclusion principle (Level 4)
20. Perturbation theory
    1. Fermi's golden rule
21. Planck postulate
22. Position and momentum spaces
23. Probability amplitude
24. Quantization (physics)
25. Quantum chromodynamics (Level 4)
26. Quantum electrodynamics (Level 4)
    1. Wheeler–Feynman absorber theory
27. Quantum entanglement (Level 4)
    1. Bell's theorem
       1. Bell test
    2. Einstein–Podolsky–Rosen paradox
    3. Problem of time
    4. Quantum nonlocality
28. Quantum field theory (Level 4)
    1. Casimir effect
    2. Conformal field theory
    3. Propagator
    4. Quantum vacuum state
       1. QCD vacuum
       2. QED vacuum
29. Quantum fluctuation
    1. Quantum foam
30. Quantum gravity (Level 4)
    1. Loop quantum gravity
31. Quantum harmonic oscillator
32. Quantum indeterminacy
33. Quantum number
34. Quantum state
    1. Bound state
    2. Excited state
    3. Ground state
       1. Topological order
    4. Stationary state
    5. Virtual state
35. Quantum superposition
36. Quantum tunnelling (Level 4)
37. Relativistic quantum mechanics
38. Schrödinger equation (Level 4)
39. Stern–Gerlach experiment
40. Symmetry in quantum mechanics
41. Uncertainty principle (Level 4)
42. Wave function (Level 4)
    1. Wave function collapse
43. Wave–particle duality (Level 4)
    1. Compton wavelength
    2. Davisson–Germer experiment
    3. Electron diffraction
       1. Double-slit experiment
    4. Matter wave
44. WKB approximation
45. Zero-point energy
46. Variational method (quantum mechanics)

This section contains 45 articles.

This section contains 96 articles.

1. Classical mechanics (Level 3)
   1. Analytical mechanics
   2. Hamiltonian mechanics (Level 4)
      1. Poisson bracket
   3. Lagrangian mechanics (Level 4)
      1. D'Alembert's principle
      2. Euler–Lagrange equation
      3. Generalized coordinates
      4. Virtual work
2. Mass (Level 3)
   1. Reduced mass
   2. Density (Level 4)
   3. Center of mass
   4. Conservation of mass (Level 4)
3. Momentum (Level 3)
4. Force (Level 3)
5. Motion (Level 3)
   1. Newton's laws of motion (Level 3)
      1. Newtonian dynamics
   2. Position (geometry)
   3. Speed (Level 4)
   4. Velocity (Level 4)
   5. Acceleration (Level 4)
   6. Jerk (physics)
   7. Equations of motion (Level 4)
      1. Constant of motion
   8. Linear motion
   9. Circular motion
   10. Projectile motion
   11. Trajectory
   12. Bouncing ball
   13. Equations for a falling body
   14. Free fall
   15. Steady state
6. Kinetic energy (Level 4)
7. Potential energy (Level 4)
   1. Potential well
8. Scalar potential
   1. Equipotential
9. Vector potential
10. Moment (physics)
11. Inertia (Level 4)
12. Moment of inertia (Level 4)
13. Friction (Level 4)
    1. Rolling resistance
14. Impulse (physics) (Level 4)
15. Power (physics) (Level 4)
16. Work (physics) (Level 4)
17. Action (physics)
18. Angular displacement
19. Angular frequency
20. Angular velocity
21. Angular acceleration
    1. Angular momentum (Level 4)
    2. Centripetal force (Level 4)
22. Rotation (Level 4)
23. Rolling
24. Torque (Level 4)
25. Weight (Level 4)
    1. Weighing scale (Level 4)
26. Frame of reference (Level 4)
    1. Inertial frame of reference
    2. Non-inertial reference frame
27. Newton's law of universal gravitation (Level 4)
    1. Cavendish experiment
28. Fictitious force
    1. Centrifugal force
    2. Coriolis force (Level 4)
29. Free body diagram
    1. Net force
30. Central force
31. Restoring force
32. n-body problem
    1. Two-body problem
       1. Kepler problem
33. Radiation pressure
34. Gravitational field
35. Gravitational potential
36. Tidal force
37. Impact (mechanics)
38. Precession
39. Vibration
    1. Mechanical resonance
40. Damping
41. Conservative force
42. Force field (physics)
43. Normal force
44. Canonical coordinates
45. Resultant force
46. Perpetual motion
47. Galilean transformation
    1. Absolute space and time
    2. Galilean invariance
    3. Relative velocity
48. Projectile
49. Reaction (physics)

This section contains 52 articles.

1. Fluid mechanics (Level 4)
2. Computational fluid dynamics
3. Rheology
4. Bernoulli's principle (Level 4)
5. Buoyancy (Level 4)
   1. Archimedes' principle
   2. Metacentric height
6. Convection (Level 4)
7. Drag (physics) (Level 4)
8. Diffusion (Level 4)
   1. Diffusion equation
9. Fluid dynamics (Level 4)
   1. Aerodynamics (Level 4)
   2. Flow visualization
10. Hydrostatics
    1. Communicating vessels
    2. Hydrostatic equilibrium
    3. Pascal's law
    4. Vertical pressure variation
11. Lift (force) (Level 4)
12. Navier–Stokes equations (Level 4)
    1. Berman flow
    2. Jeffery–Hamel flow
    3. Rayleigh problem
    4. Stokes problem
    5. Taylor–Culick flow
13. Osmosis (Level 4)
14. Reynolds number (Level 4)
15. Surface tension (Level 4)
16. Turbulence (Level 4)
17. Viscosity (Level 4)
18. Flow measurement
    1. Mass flow rate
    2. Volumetric flow rate
19. Flow velocity
20. Fluid
    1. Newtonian fluid
    2. Non-Newtonian fluid
21. Mass flow (life sciences)
22. Vorticity
23. Laminar flow
    1. Hagen–Poiseuille equation
24. Compressible flow
25. Incompressible flow
26. Deformation (physics)
27. Boundary layer
28. Euler equations (fluid dynamics)
29. Circulation (physics)
    1. Kelvin's circulation theorem
30. Pipe flow
31. Slosh dynamics
    1. Free surface effect

This section contains 30 articles.

1. Solid mechanics (Level 4)
2. Deformation (engineering) (Level 4)
   1. Poisson's ratio
3. Elastic modulus (Level 4)
4. Elasticity (physics) (Level 4)
5. Fatigue (material) (Level 4)
6. Hooke's law (Level 4)
7. Plasticity (physics) (Level 4)
   1. Brittleness
   2. Ductility
8. Rigid body
   1. Rigid body dynamics
9. Stiffness (Level 4)
10. Strength of materials (Level 4)
11. Stress (mechanics) (Level 4)
    1. Cauchy stress tensor
    2. Compression (physics)
    3. Tension (physics)
    4. Torsion (mechanics)
    5. Shear stress
12. Shearing (physics)
13. Bulk modulus
14. Finite strain theory
15. Shear modulus
16. Young's modulus
17. Contact mechanics
18. Piezoelectricity
19. Toughness
20. Fracture toughness
21. Crystallite

This section contains 3 articles.

1. Soil mechanics
2. Angle of repose
3. Granular convection

This section contains 26 articles.

1. Statistical mechanics (Level 4)
2. Microstate (statistical mechanics)
3. Boltzmann distribution
4. Partition function (statistical mechanics)
5. Distribution function (physics)
   1. Maxwell–Boltzmann distribution
6. Density of states
7. Indistinguishable particles
8. Particle statistics
   1. Maxwell–Boltzmann statistics
   2. Bose–Einstein statistics
   3. Fermi–Dirac statistics
      1. Fermi energy
9. Entropy (statistical thermodynamics)
   1. Entropy as an arrow of time
   2. Entropy (energy dispersal)
   3. Entropy (order and disorder)
10. Ensemble (mathematical physics)
    1. Canonical ensemble
       1. Grand canonical ensemble
       2. Microcanonical ensemble
11. Maxwell's demon
12. Work (thermodynamics)
13. Molecular diffusion
14. Detailed balance
15. Fluctuation–dissipation theorem

1. Nuclear physics (Level 4)
2. Atomic nucleus (Level 4)
3. Nucleon
4. Nuclide (Level 4)
   1. Isotope (Level 4)
5. Radioactive decay (Level 3)
   1. Alpha decay
      1. Alpha particle (Level 4)
   2. Beta decay
      1. Beta particle (Level 4)
      2. COBRA Experiment
   3. Neutron radiation
   4. Decay product
   5. Half-life
   6. Decay energy
   7. Radioactive source
6. Nuclear binding energy
7. Nuclear fission (Level 4)
   1. Critical mass
8. Nuclear fusion (Level 4)
   1. Cold fusion
9. Nuclear reaction
10. Nuclear isomer
11. High-energy nuclear physics
12. Nuclear force
13. Nuclear structure
14. Nucleosynthesis (Level 4)
15. Semi-empirical mass formula
16. Nuclear magnetic resonance
    1. Electron paramagnetic resonance
    2. Magnetic resonance
    3. Nuclear magnetic resonance spectroscopy
17. Island of stability
18. Hypernucleus

This section contains 49 articles.

1. Particle physics (Level 3)
2. Standard Model (Level 3)
   1. Yang–Mills theory
      1. Yang–Mills existence and mass gap
   2. Higgs mechanism
   3. Mathematical formulation of the Standard Model
3. Physics beyond the Standard Model (Level 4)
   1. Axion
   2. Grand Unified Theory
   3. Neutrino oscillation
      1. Neutral particle oscillation
   4. String theory (Level 4)
      1. D-brane
      2. Brane
      3. M-theory
      4. String (physics)
      5. Superstring theory
   5. Supergravity
   6. Supersymmetry (Level 4)
      1. Minimal Supersymmetric Standard Model
   7. Theory of everything
   8. Unified field theory
      1. Classical unified field theories
4. Particle (Level 4)
5. Scattering (Level 4)
   1. Elastic scattering
   2. Inelastic scattering
   3. Thomson scattering
6. Annihilation
7. CP violation
8. CPT symmetry
9. Electroweak interaction
10. Hierarchy problem
11. Feynman diagram
12. Generation (particle physics)
13. Pair production
14. Particle decay
    1. Proton decay
    2. Free neutron decay
15. Discovery of the neutron
16. Charge conservation
17. QCD matter
18. Quark model
19. Scalar field theory
20. Symmetry breaking
    1. Spontaneous symmetry breaking
21. Noether's theorem
22. Baryon asymmetry
23. Vacuum energy

This section contains 12 articles.

1. Spin (physics) (Level 4)
   1. Spin-1/2
2. Baryon number
3. Lepton number
4. Color charge
5. Flavour (particle physics)
6. Strangeness
7. Isospin
8. Weak isospin
9. Hypercharge
10. Weak hypercharge
11. Chirality (physics)

This section contains 11 articles.

1. Particle accelerator (Level 4)
   1. Collider
   2. Linear particle accelerator
   3. Large Hadron Collider (Level 4)
   4. Tevatron (Level 4)
   5. Relativistic Heavy Ion Collider
   6. Synchrotron
2. Particle detector (Level 4)
   1. Semiconductor detector
   2. Cloud chamber (Level 4)
   3. Calorimeter (particle physics)

This section contains 45 articles.

This section contains 10 articles.

1. Subatomic particle (Level 3)
2. Elementary particle
3. Force carrier
4. List of particles
5. Hadron (Level 4)
   1. Eightfold way (physics)
   2. Parton (particle physics)
6. Massless particle
7. Virtual particle
8. Tachyon

This section contains 22 articles.

1. Fermion (Level 4)
2. Lepton (Level 4)
   1. Electron (Level 3)
   2. Muon (Level 4)
   3. Tau (particle) (Level 4)
   4. Neutrino (Level 4)
      1. Cowan–Reines neutrino experiment
      2. Electron neutrino
      3. Muon neutrino
      4. Tau neutrino
3. Quark (Level 4)
   1. Up quark
   2. Down quark
   3. Strange quark
   4. Charm quark
   5. Bottom quark
   6. Top quark
4. Baryon (Level 4)
   1. Neutron (Level 3)
   2. Proton (Level 3)
   3. Hyperon
5. Pentaquark

This section contains 13 articles.

1. Boson (Level 4)
2. Gauge boson (Level 4)
   1. Photon (Level 3)
      1. Biophoton
   2. Gluon (Level 4)
   3. W and Z bosons (Level 4)
   4. Graviton
3. Higgs boson (Level 4)
4. Meson (Level 4)
   1. Pion
   2. Kaon
   3. J/psi meson
5. Tetraquark

This section contains 7 articles.

1. Antimatter (Level 4)
   1. Antihydrogen
2. Antiparticle (Level 4)
   1. Positron (Level 4)
      1. Electron–positron annihilation
   2. Antiproton
   3. Antineutron

1. Thermodynamics (Level 3)
2. Heat (Level 3)
   1. Cold
3. Temperature (Level 3)
   1. Thermodynamic temperature
   2. Absolute zero (Level 4)
4. Pressure (Level 4)
   1. Internal pressure
   2. Partial pressure
   3. Pressure gradient
   4. Pressure–volume diagram
5. Particle number
6. Laws of thermodynamics (Level 4)
   1. Zeroth law of thermodynamics
   2. First law of thermodynamics
   3. Second law of thermodynamics
   4. Third law of thermodynamics
7. Fundamental thermodynamic relation
8. Heat capacity (Level 4)
   1. Heat capacity ratio
   2. Specific heat capacity
9. Latent heat
10. Heat transfer (Level 4)
    1. Heat equation
    2. Thermal conduction
    3. Convection (heat transfer)
    4. Thermal radiation
    5. Newton's law of cooling
11. Entropy (Level 4)
    1. Introduction to entropy
    2. Entropy (classical thermodynamics)
    3. Boltzmann's entropy formula
12. Internal energy (Level 4)
13. Thermodynamic cycle (Level 4)
    1. Brayton cycle
    2. Carnot cycle
    3. Diesel cycle
    4. Ericsson cycle
    5. Heat pump and refrigeration cycle
    6. Otto cycle
    7. Rankine cycle
    8. Stirling cycle
14. Thermodynamic free energy (Level 4)
15. Ideal gas
    1. Ideal gas law (Level 4)
16. Heat engine
    1. Carnot heat engine
    2. Stirling engine
17. Energy conversion efficiency
18. Kinetic theory of gases
    1. Effusion
    2. Mean free path
19. Thermodynamic state
    1. Equation of state
       1. Van der Waals equation
       2. Redlich–Kwong equation of state
       3. Virial expansion
20. Thermal conductivity and resistivity
21. Thermodynamic equilibrium
    1. Equilibrium thermodynamics
22. Thermodynamic potential
    1. Enthalpy (Level 4)
       1. Enthalpy of vaporization
    2. Helmholtz free energy
    3. Gibbs free energy
23. Black-body radiation (Level 4)
    1. Black body
    2. Planck's law
    3. Planckian locus
    4. Stefan–Boltzmann law
    5. Ultraviolet catastrophe
    6. Wien approximation
    7. Wien's displacement law
24. Equipartition theorem
25. Thermodynamic process
    1. Adiabatic process
    2. Isenthalpic process
       1. Joule–Thomson effect
    3. Isothermal process
    4. Endothermic process
    5. Exothermic process
    6. Quasistatic process
    7. Reversible process (thermodynamics)
    8. Irreversible process
26. Chemical potential
27. Intensive and extensive properties
28. Thermodynamic system
    1. Closed system
29. Brownian motion
30. Photon gas
31. Entropy of mixing
32. Fluctuation theorem
33. Thermal energy
34. Thermal equilibrium
35. Thermodynamic equations
36. Boltzmann equation
    1. H-theorem
    2. Loschmidt's paradox
37. Maxwell relations
38. Thermal expansion
39. Thermal fluctuations
40. Thermodynamic limit

1. Wave (Level 3)
   1. Transverse wave
   2. Longitudinal wave
2. Mechanical wave
3. Acoustics (Level 4)
   1. Sound (Level 3)
      1. Speed of sound (Level 4)
      2. Sonic boom
      3. Sound pressure
      4. Loudness
   2. Ultrasound (Level 4)
   3. Beat (acoustics)
   4. Echo
   5. Acoustic resonance
4. Amplitude (Level 4)
5. Phase (waves)
6. Frequency (Level 4)
7. Wavelength (Level 4)
8. Wavenumber
9. Wave vector
10. Diffraction (Level 4)
    1. Diffraction-limited system
    2. Fraunhofer diffraction
    3. Huygens–Fresnel principle
       1. Fermat's principle
    4. Bragg's law
11. Doppler effect (Level 4)
    1. Relativistic Doppler effect
12. Wave interference (Level 4)
13. Noise (Level 4)
14. Resonance (Level 4)
15. Superposition principle (Level 4)
16. Wave equation (Level 4)
17. Node (physics)
18. Radio frequency
19. Wavefront
20. Harmonic
21. Pulse (physics)
22. Group velocity
23. Phase velocity
24. Shock wave
25. Waveform
26. Coherence (physics)
27. Standing wave
28. Wave packet
29. Dispersion (water waves)
30. Plane wave

This section contains 52 articles.

1. Optics (Level 3)
2. Geometrical optics
   1. Caustic (optics)
   2. Optical path
      1. Optical path length
   3. Ray (optics)
3. Physical optics
4. Focus (optics) (Level 4)
5. Focal length (Level 4)
6. Optical aberration
   1. Chromatic aberration
   2. Spherical aberration
7. Photonics
8. Polarization (waves) (Level 4)
   1. Circular polarization
   2. Linear polarization
   3. Stokes parameters
9. Reflection (physics) (Level 4)
   1. Curved mirror
   2. Reflection coefficient
   3. Transmission coefficient
   4. Total internal reflection
10. Refraction (Level 4)
    1. Photonic crystal
    2. Refractive index (Level 4)
    3. Snell's law
11. Transparency and translucency (Level 4)
12. Opacity
13. Optical depth
14. Optical power
15. Fresnel equations
16. Nonlinear optics
17. Birefringence
    1. Dichroism
18. Intensity (physics)
19. Rayleigh scattering
20. Aperture
21. Angle of incidence (optics)
22. Virtual image
23. Dispersion (optics)
24. Shadow
25. Beer–Lambert law
26. Fourier optics
27. Invisibility
28. Iridescence
29. Magnification
30. Moiré pattern
31. Photometry (optics)
    1. Illuminance
    2. Luminance
    3. Luminous flux
    4. Luminous intensity