もう

もう is a versatile adverb with several related meanings.

Usage

1. Already: An action/state completed earlier than expected
2. Anymore (with negatives): No longer, not from now on
3. More/another: An additional amount

Common patterns

• もう〜した: already did ~
• もう〜ない: not ~ anymore
• もう一(いっ)回(かい): one more time
• もう少(すこ)し: a little more
• もう一(ひと)つ: one more (thing)

Similar words

• もう vs. まだ: "already" vs. "still/not yet"
• もう食(た)べた (already ate) vs. まだ食(た)べていない (haven't eaten yet)

USAGE (telling the senses apart):
The surrounding grammar decides which meaning もう has. With a past or completed form it means "already"; with a negative it means "anymore"; directly before a number or quantity word it means "more."

WORD ORDER (sense 3): もう comes immediately before the amount, never after it — もう少(すこ)し, もう一(ひと)つ, もう一(いっ)回(かい). The reverse order is ungrammatical.

USAGE (exclamation):
On its own, drawn out as もう〜, it works as an exclamation of exasperation, roughly "oh, come on" or "geez." This is casual speech only.