Δ meaning in mathematics

Question

I am reading an article for percentage calculations...

"This means that if you want to calculate the price change in a given stock, you subtract the current price from yesterday's closing price and then divide by yesterday's closing price, and then, finally, multiply by 100 to express that number as a percentage."

ΔPrice / YesterdayClose * 100

and I am wondering what is the meaning of Δ

Answer 1

$\Delta$ means "Change in". So if $P=$price, $\Delta P = P_{start} - P_{end}$

Answer 2

In mathematics $\Delta$ usually represents a difference between two quantities. In this case, from the context of the problem, it looks likely that $\Delta \text{Price}$ represents the current price minus yesterday's closing price.