Definition: The fourth letter of the modern Greek alphabet Δ, δ.

Alright class, settle down, let’s take a peek, At a symbol that you need to speak! “Delta” – it’s a word we often see, A letter from ancient Greece, you agree? The fourth one in the script so grand, Represented with a triangle, close at hand. Δ, δ. Now what does “delta” truly mean, you ask? Let's think about this, don’t be rash! It can stand for change , a shift, or flow, Like in weather patterns – watch it grow! (Think of "delta" in the Mississippi wide,) A measure of how much things have tried To rise or fall, to move and bend, A difference measured ‘til the end. It's also used in math, you see, For change in a function, constantly! So remember Delta – Δ, δ, it’s true, Means change - let that knowledge accrue! Do you have any questions for me? Let's discuss with glee!