- - Lap in

"The word "interjection" literally means "thrown in between" from the Latin inter ("between") and iacere ("throw"). Interjections are generally uninflected function words and have sometimes been seen as sentence-words, because they can replace or be replaced by a whole sentence (they are holophrastic). Sometimes, however, interjections combine with other words to form sentences, but not with finite verbs. When an exclamation point is not needed, a comma can take the place." /wikipedia/