Interjections are definitely the most disregarded word
class and always have been. When the Greek grammarian Dionysius Thrax came up with the idea of dividing language into parts of speech
in about 100 B.C., he didn`t include interjections, and his English-language heirs have tended to do so. In the 18th century, John Horne Tooke decried «the brutish, inarticulate Interjection, which has nothing to do with speech, and is only the miserable refuge of the speechless. … The neighing of a horse, the lowing of a cow, the barking of a dog, the purring of a cat, sneezing, coughing, groaning, shrieking, and every other involuntary convulsion with oral sound, have almost as good a title to be called Parts of Speech, as Interjections have.
Lexicographers, meanwhile, have given this category short shrift because dictionaries have always emphasized the written word, while the home turf of interjections
Today the enmity persists. The compilers of the authoritative, 1,842-page Cambridge
Grammar of the English Language, published in 2002, dispense with interjections in five sentences. The Merriam-Webster dictionary
has been choosing the top 10 words of the year since 2003 and no interjection has ever made the list. The American Dialect Society has picked a single Word of the Year since 1990 and just once has an interjection got the nod: not! in 1992.
Despite the grammarians` contempt, interjections are widely used in discourse of various kinds. Uh, er, and um, in particular, have been flagrantly overused by feature writers and columnists to signal an impending attempt at irony or humor; the maneuver is now well beyond cliche, somewhere in the neighborhood of desperation. President Reagan, famous for beginning his debate responses with the interjection «Well», is a good example to illustrate the use of interjections as filler, to make a more comfortable transition to the speaker`s (or writer`s) next point.
The Internet, where writing and talking sometimes seem to merge, emphasizes this. Interjections are suitable for online writing because of the way online writing mimics speech. One of the most frequently used nowadays is meh which has no definition
in the Oxford English Dictionary
but 173 separate ones on urbandictionary.com, including: «A random word when people either don`t know what to say, don`t care, can`t answer a question or are too drunk to form a coherent English phrase.» Meh—which can also be used as an adjective, e.g., «I felt kind of meh about the whole thing.»