You can't put a period on that (in gramatically-correct English) because it isn't a sentence. You can't have a sentence without a verb. There's no verb here. If

You can't put a period on that (in gramatically-correct English) because it isn't a sentence. You can't have a sentence without a verb. There's no verb here. If you look through a real dictionary you'll also notice that the definitions are not period-terminated sentences, and this is why