How to say "phase" in Japanese

• 段階だんかいJLPT N2approx.Common
  nounCovers the process sense of 'phase': a discrete stage or step in something developing step by step, as in the early phase of a plan, a project, or an illness.
  病気びょうきはまだ初期しょきの段階だんかいです。↗

  The disease is still in the primary stage.
• 位相いそうCommon
  nounStrictly the technical, scientific sense of 'phase' in physics: the phase of a wave, of alternating current, or of the moon. Never use it for stages of a process.
• 様相ようそうJLPT N1approx.Common
  nounMeans aspect or overall appearance first; 'phase' is a secondary gloss. It points to how a situation looks rather than to a stage in it, so it is seldom the word you want for 'phase'.
  コンピューターが産業さんぎょうの様相ようそうを大おおきく変かえた。↗

  Computers have changed the industrial picture considerably.
• 時期じきJLPT N3approx.Common
  noun, adverbThe time sense of 'phase': a period or season during which something happens, as in a difficult phase one goes through. Choose it when the emphasis is on when, not on which step.
  １年ねんのこの時期じきは天候てんこうがよく変かわる。↗

  The weather changes very often at this time of year.
• 局面きょくめんCommon
  nounA phase of a developing situation or game of circumstances: situation, stage, or phase, as in the situation entering a new phase. Suited to affairs, negotiations, and other unfolding matters.
  われわれは局面きょくめんの打開だかいを図はからなくてはならない。↗

  We must try to break the deadlock.

Use 段階 for stages in a process, 時期 for a period of time, 局面 for a phase of an unfolding situation, 位相 only for scientific phase (waves, electricity, the moon), and 様相 mainly for aspect or appearance.

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

• 段階だんかいstage
• 位相いそうphase (e.g. wave, electricity, moon)
• 様相ようそうaspect
• 時期じきtime
• フェーズphase
• 部面ぶめんphase
• 事相じそうaspect
• 盈虚えいきょwaxing and waning (of the moon)
• 病相びょうそうepisode (of a mental illness)
• 局面きょくめんsituation
• 段だんstage (in a process)
• 相そうphase (e.g. solid, liquid and gaseous)