Definition · Plain-language
Interjection
An interjection is a word or short phrase that expresses a sudden emotion or reaction — words such as wow, ouch, oh and hey — and stands largely apart from the grammar of a sentence.
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What interjections express
An interjection conveys an immediate emotion or reaction rather than describing or connecting like other words. Different interjections carry different feelings: wow and ooh signal surprise or wonder; ouch and ow signal pain; yuck and ugh signal disgust; hooray and yay signal joy; oh and well signal hesitation or thought; hey signals a call for attention. Some, such as hmm and um, are fillers that mark thinking or pausing in speech. Because they express feeling directly, interjections are far more common in conversation and dialogue than in essays or reports, where a writer would usually convey the emotion through description instead.
Grammatical independence and punctuation
What sets the interjection apart from the other parts of speech is that it stands largely outside the grammar of the sentence. You can remove an interjection and the remaining sentence is still complete: in "Wow, that was fast", the clause "that was fast" needs nothing from "wow". Punctuation reflects this independence. A mild interjection is usually set off with a comma ("Well, I suppose so"), while a strong one often takes an exclamation mark and may stand alone as its own sentence ("Ouch! That hurt."). This separateness is why interjections are sometimes described as the most loosely attached of the eight parts of speech.
Register and use in writing
Interjections belong mainly to informal English. They bring energy and a natural, spoken feel to dialogue, social media and casual writing, which is exactly why they are usually avoided in academic and professional prose, where a measured, impersonal tone is expected. In formal writing, the emotion an interjection would convey is better expressed through word choice and sentence structure. When interjections are used, they should be deployed sparingly; a passage peppered with "wow" and "oh" quickly feels overwrought. Understanding the interjection completes the traditional set of eight parts of speech, even though it is the one least involved in sentence structure.
Key facts
At a glance
- Definition: a word or phrase expressing sudden emotion or reaction
- Examples: wow, ouch, oh, hey, oops, hooray, ugh
- Grammar: stands apart — not grammatically linked to the sentence
- Punctuation: set off by a comma, or marked with an exclamation point
- Register: common in speech and informal writing; rare in formal prose
- Status: one of the eight traditional parts of speech
Common misconceptions
What people often get wrong
Often heard: An interjection is grammatically connected to the rest of the sentence.
Actually: Interjections stand apart. Remove one and the sentence is still complete: in "Oh, I see", the clause "I see" needs nothing from "oh", which is why interjections are punctuated separately.
Often heard: Interjections are fine to use freely in formal academic writing.
Actually: Interjections belong mainly to speech and informal writing. Formal prose usually avoids them, conveying emotion through word choice and structure instead.
Often heard: An interjection must always be followed by an exclamation mark.
Actually: Only strong interjections typically take an exclamation mark. Milder ones are set off with a comma, as in "Well, that is interesting."
Going deeper
