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one; 1
best
first; foremost
beginning; start
a (single); one (of many)
ace
bottom string (on a shamisen, etc.)
壱から数え直しましょう。
Let's count again from one.
あと壱つだけ質問があります。
I have just one more question.
壱番前の席に座ってくれると助かります。
It would help if you sat in the front seat.