The interjection is a grammatically unchangeable part of speech that ex­presses human emotions, states of mood and volition without naming them. The latter property makes it possible for some scholars to contrast interjec­tions with so-called “intellectual words”.

Interjections differ from all other parts of speech in their origin, specific nomination, phonetic structure as well as in a number of semantic, morpho­logical and syntactic properties.

The important feature of interjections is their generalized meaning. In writing, the meaning of an interjection is revealed in utterances, preceding or following an interjection, in authors’ remarks. In oral communication the meaning of an interjection is specified by the speakers’ intonation, facial expression, or gestures. As a result, a context, a situation, extralinguistic means only help to single out interjections but also to clarify their meanings, for most English interjections are polysemantic. For example, the interjection oh may express such diverse emotions as astonishment, joy, entreaty, etc.

Morphologically, the interjection as part of speech is rather amorphous. Heated disputes still continue concerning the corpus of interjections and lin­guistic works on interjections show significant divergence in interpretations of this part of speech. Among other suggestions, some grammarians argue that politeness formulas and greetings should be treated as interjections. Other scientists argue that these language units do not express the speakers’ emotions, though sometimes they may convey emotional colouring. Moreo­ver, components within these expressions retain their lexical meaning. Be­sides, grammatically, these word combinations may be interpreted as parts of other, larger constructions: Good morning (I wish you good morning), thank you (I thank you), Goodbye (May God be with you), etc. Thus, at present, the linguistic status of politeness formulas is hardly specified.

Onomatopoeic words do not express any emotions or volition either, though they may be very similar to interjections when other properties arc concerned. It should be mentioned, however, that the borderline between the former and the latter is not absolute, which results in transition of some ono­matopoeic words into interjections, e.g. boo, humph, pooh, phew, ugh, yuk.