Refers to a pocket in clothing, bags, or similar items. Also used in compound words like ポケットティッシュ (pocket tissue).
上着のポケットに鍵を入れた。
I put the key in my jacket pocket.
このズボンにはポケットがたくさん付いている。
These pants have a lot of pockets.
I put the key in my pocket.
He took his phone out of his pocket.
It was cold, so I walked with my hands in my pockets.
pocket square; decorative handkerchief
pocket knife