1A number within a sequence, an ordinal or index used to identify position (as in 'what number').
受付で番号札をもらって、番が来るまで待った。
I got a number ticket at the reception and waited until my number was called.
彼の席は教室の三番だ。
His seat is number three in the classroom.
何番のバスに乗れば駅に着きますか。
Which numbered bus should I take to get to the station?
2One's turn to act, the point in a sequence when it becomes someone's turn.
次は私の番だから、しばらく待っててください。
It's my turn next, so please wait a bit.
お皿を洗うのは今日は君の番だよ。
Today it's your turn to wash the dishes.
順番が回ってきたので、名前を呼ばれた。
When my turn came around, my name was called.
3A watch, guard, or lookout duty, the act of keeping watch over something (as in 'to stand guard').
夜の番を交代でやっているので安心だ。
We take turns standing watch at night, so it's reassuring.
倉庫の番をする人が一晩中見回りをした。
The person on guard at the warehouse made rounds all night.
4As a suffix, indicates rank, standing, or position (e.g., 一番 'the most', ～番目 'the nth position').
彼はチームでいつも一番速い走者だ。
He is always the fastest runner on the team.
席は左から三番目に座ってください。
Please sit in the third seat from the left.
5A bout or match, especially in contexts like sumo, one individual contest.
今日は横綱同士の見ごたえのある一番がある。
Today there's an exciting bout between two yokozuna.
その一番に勝てば、優勝が決まる。
If he wins that bout, the championship will be decided.
6A number indicating a piece within a collection, used like 'No. ~' (e.g., 'Symphony No. 9').
ベートーヴェンの交響曲第九番は有名だ。
Beethoven's Symphony No. 9 is famous.