if; in case; supposing
「若し」 has another reading with different meanings.
like; as if; the same as
もし明日雨だったら行きません。
If it rains, I won't go.
もし暇なら来てください。
If you're free, please come.
もしよければ手伝った方がいい。
If you don't mind, please help.