In chemistry, what do the delta symbols Δ and δ stand for?

Δ means "the change in", and δ means "a small amount of".

Delta is the fourth letter in the Greek alphabet.

The capital letter Δ corresponds to the English letter D, and the lowercase δ corresponds to the English letter d.

In chemistry, Δ means "the change in". Thus, ##ΔT## means "the change in ##T##", ##ΔE## means "the change in ##E##", and so on.

If the temperature changes from 270 K to 300 K, we sat that the change in temperature ##ΔT## = 300 K – 270 K = 30 K.

We also say that the slope of a straight line is " the change in ##y## divided by the change in ##x##". We write this as

##"slope" = (Δy)/(Δx)##.

The lowercase δ usually means "a small amount". It is often used to show a partial electrical charge on an atom.

For example, in a polar H-F bond, we might say that the more negative F atom has a ##δ^-## partial charge. The H atom would then have a ##δ^+## partial charge.