1A conditional adverb placed at the head of a clause to set up a hypothetical or supposition; typically pairs with a following conditional form (…たら, …なら, …ば) to mean 'if …'. Usually written in kana.
もし雨が降ったら、試合は中止です。
If it rains, the match will be cancelled.
もし宝くじが当たったら、何を買いますか。
If you won the lottery, what would you buy?
もし何か困ったことがあれば、いつでも連絡してください。
If you ever run into any trouble, contact me anytime.
もし私があなたなら、その仕事は引き受けないでしょう。
If I were you, I wouldn't take that job.
もし間に合わないようなら、先に始めておきます。
If it looks like you won't make it in time, I'll go ahead and start.