Interjection

In linguistics, an interjection is a word or expression that occurs as an utterance on its own and expresses a spontaneous feeling or reaction. The category is quite heterogeneous, and includes such things as exclamations (ouch!, wow!), greetings (hey, bye), response particles (okay, oh!, m-hm, huh?), and hesitation markers (uh, er, um). Due to its heterogeneous nature, the category of interjections partly overlaps with categories like profanities, discourse markers and fillers.

Interjections may be subdivided and classified in several ways. A common distinction is based on relations to other word categories: primary interjections are interjections first and foremost (examples: , Ouch!, Huh?), while secondary interjections are words from other categories that come to be used as interjections in virtue of their meaning Another distinction based on form is between interjections that are single words ('Oh!', 'Wow!') versus those that are phrases ('sup!' from 'What's up?', 'Excuse me!, 'Oh dear!').

Further distinctions can be made based on function. Exclamations and curses are primarily about giving expression to private feelings or emotions, while response particles and hesitation markers are primarily directed at managing the flow of social interaction.

Interjections can take very different forms and meanings across cultures. For instance, the English interjections gee and wow have no direct equivalent in Polish, and the closest equivalent for Polish fu (an interjection of disgust) is the different sounding Yuck!. Curses likewise are famously language-specific and colourful. On the other hand, interjections that manage social interaction may be more similar across languages. For instance, the word 'Huh?', used when one has not caught what someone just said, is remarkably similar in 31 spoken languages around the world, prompting claims that it may be a universal word. Similar observations have been made for the interjections 'Oh!' (meaning, roughly, now I see) and 'Mm/m-hm' (with the meaning 'keep talking, I'm with you').

Across languages, interjections often use special sounds and syllable types that are not commonly used in other parts of the vocabulary. For instance, interjections like brr and shh! are made entirely of consonants, where in virtually all languages, words have to feature at least one vowel-like element. Some, like 'tut-tut' and 'ahem', are written like normal words, but their actual production involves clicks or throat-clearing. The phonetic atypicality of some interjections is one reason they have traditionally been considered as lying outside the realm of language.

...
Wikipedia