How to say "complex" in Japanese

Choosing the right word
  • 複雑ふくざつJLPT N4approx.Common
    na-adjective, nounThe general word for something with many interrelated parts — a complex problem, structure, or situation. It also covers 'mixed (feelings)', as when conflicting emotions leave you unable to say how you feel.
    あれはとても複雑ふくざつな機械きかいだ。↗
    That is a very complex machine.
  • nounThe psychological sense only: a deep-seated feeling of inferiority or fixation about something. It never describes a problem or system as complicated, so it is the wrong choice for that sense.
  • ややこしいJLPT N1approx.Common
    i-adjectiveComplicated in the sense of confusingly tangled: rules, explanations, or situations so knotted that they are hard to follow, with the emphasis on the confusion they cause.
    あの5人にんの関係かんけいは、ややこしい。↗
    The relationships among those five people are complicated.
  • 複合ふくごうJLPT N1approx.Common
    suru verb, no-adjective, transitive verb, intransitive verbReally means composite or combined — something made of several elements together — rather than 'complex' in the ordinary sense. It is a marginal rendering of complex; choose it only when the combined-elements meaning is intended.
  • 煩雑はんざつCommon
    na-adjective, nounComplicated in a cumbersome, confusing way — typically procedures, paperwork, or arrangements that are a hassle to deal with. Use it when the complexity is a burden, not just intricate.
    マウスとキーボードを行おこなったりきたりするのが煩雑はんざつなので、キーボードのみで操作そうさできるようショートカットキーはないのでしょうか?↗
    It's a fiddle going to and fro between the keyboard and mouse so are there shortcuts to allow operation using only the keyboard?

Use 複雑 for the general 'complex/complicated' sense (including mixed feelings), 「コンプレックス」 for the psychological sense, 「ややこしい」 for confusingly tangled cases, 複合 for composite things, and 煩雑 for cumbersome complications.

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

Japanese equivalents
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JLPT vocabulary levels are community estimates, not official (no official lists have been published since the 2010 revision).

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