Using "ab" would lead to ambiguity, since it could mean "a*b". Also, there is no reason for using two letter variables when you can use any letter from the lati

Using "ab" would lead to ambiguity, since it could mean "a*b". Also, there is no reason for using two letter variables when you can use any letter from the latin or greek alphabet, with any notation like ä or â or even create your new symbols like ∫, ℝ or ℕ when nothing matches the concept you want to express. Unlike programming languages, math notation evolved without being constrained by monospace ASCII characters and text lines.