one copy (of a document); one letter
one-way traffic
《mahjong》pure straight; winning hand containing nine consecutive tiles of the same suit (i.e. 1-9)
一通の手紙を書いた。
I wrote one letter.
契約書を一通作成した。
I prepared one copy of the contract.
一通の証明書が必要だ。
One copy of a certificate is needed.