adjectival noun or quasi-adjective

必用 can imply has to be used rather than is just needed.
  1. necessary, needed, essential, indispensable.

noun

  1. necessity, need, requirement.

Variations

Pronunciation Kanji Kana Is Common
必要 ひつよう
必用 ひつよう

Contained Kanji Breakdown

invariably, certain, inevitable
ヒツ かなら.ず (4th, N3)
heart, mind, spirit
こころ シン (2nd, N4)
katakana no radical (no. 4)
ヘツ えい よう (Kentei 1)
need, main point, essence
ヨウ い.る かなめ (4th, N3)
variant of radical 146
woman, female
ジョ おんな め (1st, N5)