〜と

Conditional と connects a triggering action to its automatic, predictable, natural consequence — "whenever X, [it follows that] Y." 春になると、桜が咲く — "When spring comes, the cherry blossoms bloom."

This is the conditional with the least speaker volition in the consequence clause. The Y clause is something the speaker presents as inevitable, mechanical, or general-truth-like. Compare:
• Cherry blossoms bloom in spring → と (natural law)
• Press the button, lights turn on → と (machine behavior)

Because Y is presented as automatic, と sounds wrong when Y expresses intention, command, request, or invitation: ✗ 春になると、出かけよう ("when spring comes, let's go out") doesn't work — switch to たら or ば. This is the most common と pitfall.

Note: this と is the conditional conjunction — it attaches to verbs in plain non-past form. It's spelled the same as the particle と ("with / and / quotation") but has a different syntactic position and meaning. The descriptive slug conditional-to here distinguishes it from particle-to.