ΔT

ΔT is the time difference between Universal Time, a time scale based on the Earth's non-uniform rotation, and Terrestrial Time, a uniform time scale currently based on the caesium atomic clock.

The term is used to represent other time differences:

• The interval of time used in determining velocity.
• The increment between successive nerve impulses.

The term is also used to represent differences or changes of temperature:

• In discussions of climate change.
• In discussions of heat transfer.
• In discussions of the effects of Thermal gradients.