If is used to introduce a condition, showing that one thing depends on another, as in "If it rains, we’ll stay inside." It can also introduce something imagined or uncertain.
From Old English "gif" meaning "if, whether," related to other Germanic conditional words. Over time, English spelling and pronunciation shifted it into the small but powerful word we use today.
That tiny word "if" is the doorway to every alternate future you can imagine—it’s how we mentally test reality before acting. In logic and programming, whole systems of reasoning are built out of nothing more than chains of "if" statements.
Complete word intelligence in one call. Free tier — 50 lookups/day.