The word interjection comes from Latin, and literally means something “thrown between.” In English, interjections are expressions of emotion. They don’t normally modify anything else in the sentence.
Interjections are common in everyday speech, but should be avoided in formal writing.
Here are some examples of interjections:
Oh, uh, um, eh, hey, ah, etc.
gosh, golly, etc.
alas, alack, etc.
Mild interjections can be set off with commas. Stronger expressions of emotion are often followed by an exclamation point. If an interjection comes in the middle of a sentence, you might place dashes around it.
Here are some examples of how you might punctuate various interjections:
Gee whiz, I never thought of that!
Ouch! Watch your step!
Okay, next goal wins!
She said “bye” and waved.
And we all know—hallelujah!—that we are saved by faith in our good works.
Your contribution to our project has been, well, not the greatest.