もし

もし
adverb
if; in case
descriptive
1. if; in case
Introduces a hypothetical condition, typically used with conditional forms like ～たら or ～ば.
もし雨(あめ)が降(ふ)ったら、行(い)きません。
If it rains, I won't go.
もし時間(じかん)があれば、手伝(てつだ)ってください。
If you have time, please help me.
もしよかったら、一緒(いっしょ)に行(い)きませんか。
If you'd like, would you like to go together?
Polite invitation
もし明日(あした)天気(てんき)がよかったら、公園(こうえん)でお弁当(べんとう)を食(た)べませんか。
If the weather is nice tomorrow, shall we eat boxed lunches in the park?
もし日本(にほん)に住(す)むことになったら、どこに住(す)みたいか考(かんが)えたことがありますか。
Have you ever thought about where you would want to live if you were to live in Japan?

もし marks a hypothetical condition and is typically paired with conditional forms.

Conditional pairs

  • もし〜たら: if ~ (most common, neutral)
  • もし〜ば: if ~ (slightly formal)
  • もし〜なら: if ~ (topical, "speaking of")
  • もし〜としたら: supposing that ~

Common expressions

Optionality

もし is optional—conditionals work without it. Adding もし emphasizes the hypothetical nature or adds politeness.

雨(あめ)が降(ふ)ったら... = If it rains...
もし雨(あめ)が降(ふ)ったら... = If it were to rain...

Usage

もし is an adverb, so it appears before the condition, not after.

Related Words

Related: もしも (emphatic form)
Related: 仮(かり)に (supposing, hypothetically)
Compare: 例(たと)え (example)
core
Added 2026.1.8 12:55 · Revised 2026.9.4 21:29
01000/01284_moshi