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必要
hitsuyō
necessity
水は生きるために必要だ。
Water is necessary to live.
formal
Something that is essential or required; necessity.
この仕事にはパソコンが必要です。
A computer is necessary for this job.
健康は何よりも必要なものだ。
Health is the most necessary thing of all.
Can be used as a na-adjective (e.g., 必要な情報 = necessary information).
formal
Requiring something; needed.
このプロジェクトには追加の予算が必要だ。
This project requires additional funding.
Often followed by particles like に (e.g., 必要に応じて = as needed).
Pro Tip
Avoid confusion with 必要性 (hitsuyō-sei)
必要性 means "necessity" as an abstract concept (e.g., その必要性は高い = "The necessity of that is high"), while 必要 is more concrete (e.g., 必要な資料 = "necessary materials").
Gold Rule
Particle usage with 必要
When 必要 is used as a verb (e.g., "to need"), it takes に (e.g., お金が必要に = "I need money"). When used as an adjective, it modifies a noun directly (e.g., 必要なもの = "necessary things").
Word Origin
From Middle Chinese 必要 (pjet-ʔjew, "necessary, essential"). The kanji 必 (hitsu, "certainly") + 要 (yō, "important").
Usage Notes
Used in both formal and informal contexts. As a na-adjective, it often appears before nouns (e.g., 必要な書類 = necessary documents).
Word Breakdown
必
certainly, without fail
kanji要
important, essential
kanji和英辞典