刚才【gāngcái】

刚才 means "just now, a moment ago", counted from the moment of speaking. It's a time word like 今天 or 昨天: it goes before or after the subject, and always before the verb.

刚才 or 刚

刚 is an adverb. It goes after the subject only, and says something happened a short time before the moment you're talking about – which can be minutes, days or a year. 刚才 is always minutes ago, counted from now.

Because 刚才 is a time word, it does things 刚 can't. It goes before the subject, it takes 的 to describe a noun, and 不 or 没 can follow it.

刚 goes the other way: it can take a length of time after the verb, which 刚才 can't.

• × 刚我看见他了 → 刚才我看见他了
• × 刚的电话 → 刚才的电话
• × 我刚才来三天 → 我刚来三天

Something that has since changed

With 还, 刚才 describes a state that held a moment ago and has stopped.