Alliteration is the repetition of consonant sounds, as in "the forest's ferny floor" (de la Mare, The Listeners). Many English idioms and sayings are easier to remember because of alliteration. We say 'dead as a doornail', even though a 'doornail' (what is that?) is no deader than any other kind of nail - only, it may be thought, because we repeat the d sound. Impertinent people are 'as bold as brass', not 'iron' or 'gold', because two b sounds seem better than one.
In Old and Middle English (roughly from 800 - 1500), there was a form of poetry called alliterative verse, in which the pattern that in Modern English verse is usually played by rhyme was taken by the repetition of consonant sounds on stressed syllables. There are usually four 'beats' in a line, of which three fall on syllables that begin with the same letter. There may be alliteration on other, unstressed, syllables. (See also sprung rhythm.)
- Since the siege and the assault was ceasèd at Troy
said the anonymous author of Sir Gawain and the Green Knight (around 1400 CE).
- This was "Siðen ðe sege and ðe assaute watz cesed at troye" in the original spelling.
In poetry, speeches and advertising, alliteration can be used to powerful effect, to play on the reader's emotions and thoughts. Sometimes it is used to portray a scene: "the stuttering rifles' rapid rattle" (Wilfred Owen, "Anthem for Doomed Youth"). Here there is alliteration of both the '-t-' and the '-r-' sounds, which help evoke, through onomatopoeia, the sound of small-arms fire.