The symbols Δt and ΔT (spoken as "delta T") are commonly used in a variety of contexts.

• ΔT (timekeeping) the difference between two time scales, Universal Time and Terrestrial Time, which results from a drift in the length of a day
• The interval of time used in determining velocity
• The increment between successive nerve impulses

• To mean a difference in temperature including thermodynamic temperature, may occur in
  • Discussions of climate change
  • Discussions of heat transfer
  • Discussions of the effects of thermal gradients

• Delta time (disambiguation)
• Finite difference for the mathematics of the Δ operator
• Delta (letter) for the Greek letter Δ
• ∂ for the mathematical symbol used in the notation "∂T"