わざと

わざと means "on purpose": the action was meant, not an accident. It is an adverb and goes in front of the verb.

Most of the time わざと points at something mean or sneaky, so it turns up in accusations and apologies. わざとじゃない is how you say "I didn't mean to".

It can be neutral too, when someone does something deliberately for a good reason.

わざと or わざわざ

わざと is about intent: they meant to do it. わざわざ is about effort: they took the trouble to do it, often for you.

• × わざと来てくれてありがとう → わざわざ来てくれてありがとう