An interjection has been defined to be, “that part of speech which denotes some affection or emotion of the mind.” It is clearly not a necessary part of speech; for, as Tooke observes, interjections are not to be found in books of history, philosophy, or religion: they occur in novels only, or dramatic compositions. Some of these are entirely instinctive and mechanical, as, ha! ha! ha! sounds common to all men, when agitated with laughter. These physical emissions of sound have no more claim to be called parts of speech than the neighing of a horse, or the lowing of a cow. There are others which seem arbitrary, and are expressive of some emotion, not simply by the articulation, but by the accompanying voice or gesture. Grief, for example, is expressed in English by the word ah! or oh! in Latin by oi, ei! and in Greek by οἶ, οἶ, αἶ, αἶ! Here the sounds are not instinctive, or purely mechanical, as in laughing; but the accompanying tone of voice, which is the same in all men, under the influence of the same emotion, indicates clearly the feeling or passion of the speaker. Others, which have been deemed interjections, are, in truth, verbs or nouns, employed in the rapidity of thought and expression, and under the influence of strong emotion, to denote, what would otherwise require more words to express: as, strange! for it is strange; adieu! for I recommend you to God; shame! for it is shame; welcome! for you are welcome.
The words which have been considered by our English grammarians as interjections, are the following, expressive of
1. Joy, as, Hey, Io.
2. Grief, Ah, alas, alack.
3. Wonder, Vah! hah! aha!
4. Aversion, Tush, pish, pshaw, foh, fie, pugh.
5. Laughter, Ha, ha, ha.
6. Desire of attention, Hark, lo, halloo, hem, hip.
7. Languor, Heigh ho.
8. Desire of silence, Hush, hist, mum.
9. Deliberation, Hum.
10. Exultation, Huzza.
11. Pain, Oh! ho!
12. Taking leave, Adieu.
13. Greeting, Welcome.