用いる|もちいるmochiiru[3]nakadaka (mid-high)

1. ichidan verb, transitive verbto use; to make use of; to utilize; to utilise
   この語ごは今いまでは用もちいられない。↗

   That word has fallen out of use.

• Synonym使うつかうNeutralThe everyday default for using tools, methods, money or people; 「用いる」 says the same thing but in a more written, formal register.
• Synonym使用しようNeutralNoun and verb for plain 'use', as in 「使用禁止」; typical of instructions and rules rather than everyday speech.
• Synonym利用りようNeutralUsing something for your own benefit, as in 「バスを利用する」; it can also mean exploiting a person, with a negative shade.
• Synonym運用うんようWrittenWritten word for putting funds, systems or rules into operation, as in 「資金を運用する」; the emphasis is on managing and running them.
• Synonym役立てるやくだてるNeutralTo put something to work so it actually helps, as in 「経験を役立てる」; the point is making it useful, not simply using it.
• Synonym活用かつようNeutralMaking full, effective use of someone's or something's abilities, as in 「人材を活用する」; in grammar it also means conjugation.
• Synonym行使こうしWrittenWritten word for exercising rights, authority or force, as in 「拒否権を行使する」; its objects are mostly rights and powers.
• Synonym採用さいようNeutralTo adopt an opinion or method, or to hire staff, as in 「新方式を採用する」「社員を採用する」; it implies choosing and taking on.
• Synonym採るとるNeutralTo take up a method or measure, as in 「強硬策を採る」; it also covers picking or gathering things such as flowers.
• Synonym利かすきかすNeutralTo bring out an effect or ability, as in 「機転を利かす」 or 「塩を利かす」; the stress is on making the effect show.
• Related働かせるはたらかせるNeutralTo set a person to work, or to exercise one's brain or imagination, as in 「頭を働かせる」; the focus is on making something work.
• Related当てはめるあてはめるNeutralTo fit a rule or formula onto a concrete case, as in 「公式に当てはめる」; it is about matching a case, not general use.
• Related適用てきようWrittenFormal term for applying a law or rule to a particular case, as in 「保険が適用される」.
• Antonym捨てるすてるNeutralTo throw away or give up using something — the everyday opposite of 「用いる」.
• Antonym廃するはいするWrittenWritten word for abolishing or discontinuing something, as in 「制度を廃する」; the formal opposite of 「用いる」.
• Antonym使わないNeutralThe negative of 「使う」: not to use something; the direct opposite of 「用いる」.

For everyday use, say 「使う」; 「用いる」 is the written, formal choice. Use 「利用」 when something serves your benefit, 「活用」 for making full use of something, 「適用」 for applying rules to cases, and 「採用」 for adopting a plan or hiring people.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

1. （原義げんぎ）目下めしたの者ものを、率ひきいてあることをさせる。
2. （人ひとを）登用とうようする。
3. 問題もんだいなどを解決かいけつするために、あるものを役立やくだてる。使用しようする。
4. 案あんなどを採用さいようする。
5. 注意ちゅういなどを働はたらかせる。心こころを配くばる。
6. （古いにしえ、打消うちけしの形かたちで）必要ひつようとする。