Definition of "interjection" [in•ter•jec•tion]

• A sudden, short utterance; an ejaculation. (noun)
• The part of speech that usually expresses emotion and is capable of standing alone. (noun)
• Any of the words belonging to this part of speech, such as Ugh! or Wow! (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "Like the English hail (as in “Hail to the Chief”), the German interjection comes from the Old Norse word for whole"
• "A manuscript I'm editing uses "for Christ sake" in dialogue as an interjection, which is fine in the context, but I can't find a decent reference for the most common spelling."
• "As the interjection is the least important part of speech in the English language, it will require but little attention."