一つ

• (Tokyo) ひとつ [hìtóꜜtsù] (Nakadaka – [2])^[1]
• IPA^(key): [çito̞t͡sɨ]

一(ひと)つ • (hitotsu) 

1. one thing

   ブラシを一(ひと)つ買(か)った。

   Burashi o hitotsu katta.

   I bought a brush.

一(ひと)つ (hitotsu) is used when the items counted have no specific counter category. See Wikipedia's "Japanese counter word" entry for details.

• 二つ
• Category:Japanese counters