とき— When / At the Time Of

• 困ったとき、いつでも相談してください。

  Komatta toki, itsu demo soudan shite kudasai.

  When you're in trouble, please consult me anytime.

  困った + とき = when [you are] in trouble

• 子供のとき、よく泣いていた。

  Kodomo no toki, yoku naite ita.

  When I was a child, I often cried.

  子供 + の + とき = during childhood

• ひまなとき、よく散歩をします。

  Hima na toki, yoku sanpo o shimasu.

  When I'm free, I often take walks.

  ひま (な-adj) + な + とき = when (I'm) free

• ・Tense before とき matters: 行くとき (when about to go / on the way) vs 行ったとき (when you've arrived / after going).
• ・Nouns connect with の (子供のとき), な-adjectives with な (元気なとき).
• ・とき or とき に — に pins it to a specific point in time.

Commonly confused with

The JLPT rarely asks whether you recognise a pattern — it asks which of several similar patterns fits. These are the ones とき is tested against.

• 間 (あいだ) — Throughout a Duration
• 間に (あいだに) — A Point Within a Window
• あとで — After (with a time gap)
• 頃 / ごろ — Around / About (approximate time)
• までに — By / No later than (deadline)
• 〜おきに — The Gap Logic (Intervals)
• たばかり — Just did (subjective recency)
• たところ — Just finished (this very moment)