Short greetings

HIS

Think of how you might casually acknowledge a group of friends when you see them—these three letters often stand in for their names.

"Short greetings" hints at the word "HI," a common casual greeting. The answer "HIS" takes that and adds an "S" at the end, which is a trick crossword solvers often see—turning a singular word into its possessive form. So, it’s playing on the idea of a brief greeting ("HI") being tweaked slightly to fit the answer.