also: いいかい
interjection
Casual interjection used to get someone's attention before speaking; often used when about to say something important or give instructions.
いいか、よく聞いてくれ。
Listen, listen carefully.
いいか、絶対に遅れるなよ。
Hey, don't be late, okay?
expression
Casual phrase used to remind, explain, or emphasize a point; often softens a statement or adds a persuasive tone.
いいか、これは大事なことなんだ。
You see, this is important.
いいか、約束したんだからな。
Remember, you promised.