What do they mean by delta?

When people say what do they mean by delta, they are usually asking about change, difference, or a river mouth, but you have to look at context because delta is a heavily overloaded term. In everyday business language, when someone says what is the delta, they mean what is the difference or gap between two numbers. For example, what is the delta between budget and actual, or what is the delta between last quarter and this quarter. In that case, delta means variance. In mathematics and science, they mean change, calculated as final minus initial. A teacher saying find the delta means find the difference. In geography or news, they mean a river delta, the triangular fertile land where a river meets the sea, like the Mississippi Delta. In finance and investing, especially options trading, they mean the hedge ratio, how much an option price moves for a $1 move in the stock, and also the probability of expiring in the money. In the military or when spelling, they mean the letter D, because Delta is the NATO phonetic for D. In Greek life, they mean a fraternity or sorority with Delta in its name. In tech, they mean the difference between two versions of code or files. So when someone asks what do they mean by delta, the best way to answer is to ask what field they are in, but generally assume they mean difference or change unless they are talking about rivers.