interjection
noun

- an occasion when someone interrupts someone else, or the interruptions themselves
           
- a word that is used to show a short sudden expression of emotion

Cambridge Dictionary

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An interjection is a word or expression that occurs as an utterance on its own and expresses a spontaneous feeling or reaction.

interjections include such things as:

- exclamations (ouch!, wow!)

- curses (damn!)

- greetings (hey, bye)

- response particles (okay, oh!, m-hm, huh?)

- hesitation markers (uh, er, um)

and other words (stop, cool)

The use and linguistic discussion of interjections can be traced historically through Greek and Latin over many centuries,

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SYNONYMS

exclamation, ejaculation, sudden utterance, cry, shout, roar

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SOURCES:

- Bloomfield, Leonard - Language
- Crystal, David - A dictionary of linguistics & phonetics
- Ameka, Felix K. (1992). "Interjections: The Universal Yet Neglected Part of Speech". Journal of Pragmatics.