1An errand — the act of going somewhere to carry out a task or delivery that someone has asked of you.
母に頼まれて、駅まで使いに行った。
I ran an errand to the station because my mother asked me to.
ちょっと使いを出してくるから、ここで待ってて。
I'm going to run a quick errand, so wait here.
会社の使いで領収書を取りに行った。
I went to pick up the receipt on an errand for the company.
2A messenger or bearer — someone sent to carry a message, deliver something, or perform an errand on another's behalf.
村の使いが王様からの手紙を届けに来た。
A messenger from the king came to the village to deliver a letter.
急用で使いを出したが、まだ帰ってこない。
I sent someone on an urgent errand, but they still haven't come back.
3(informal, in stories/folklore) A familiar spirit — a supernatural attendant that serves a magician or sorcerer.
物語の中で彼の使いは黒い猫だった。
In the story, his familiar was a black cat.
4A suffix meaning 'use/usage' or 'a person who handles X' — attached after a noun (e.g., 言葉づかい 'way of speaking', 魔法使い 'sorcerer'). Often pronounced づかい in this suffix use.
言葉づかいには気を付けてください。
Please be mindful of your choice of words.
彼は魔法使いの役を演じた。
He played the role of a sorcerer.
筆遣いを見れば、その人の書道の個性が分かる。
You can tell someone's calligraphy style from their brushwork.