In language
Language may refer either to the specifically human capacity for acquiring and using complex systems of communication, or to a specific instance of such a system of complex communication...

, alliteration refers to the repetition of a particular sound
In a language or dialect, a phoneme is the smallest segmental unit of sound employed to form meaningful contrasts between utterances....

 in the first syllable
A syllable is a unit of organization for a sequence of speech sounds. For example, the word water is composed of two syllables: wa and ter. A syllable is typically made up of a syllable nucleus with optional initial and final margins .Syllables are often considered the phonological "building...

s of Three or more words or phrases. Alliteration has historically developed largely through poetry
Poetry is a form of literary art in which language is used for its aesthetic and evocative qualities in addition to, or in lieu of, its apparent meaning...

, in which it more narrowly refers to the repetition of a consonant
In articulatory phonetics, a consonant is a speech sound that is articulated with complete or partial closure of the vocal tract. Examples are , pronounced with the lips; , pronounced with the front of the tongue; , pronounced with the back of the tongue; , pronounced in the throat; and ,...

 in any syllables that, according to the poem's meter
Meter (poetry)
In poetry, metre is the basic rhythmic structure of a verse or lines in verse. Many traditional verse forms prescribe a specific verse metre, or a certain set of metres alternating in a particular order. The study of metres and forms of versification is known as prosody...

, are stressed, as in James Thomson's verse "Come…dragging the lazy languid Line along".

Alliteration is usually distinguished, as and within, from the mere repetition of the same sound positions other than the beginning of each word — whether a consonant, as in "some mammals are clammy" (consonance) or a vowel, as in "yellow wedding bells" (assonance
Assonance is the repetition of vowel sounds to create internal rhyming within phrases or sentences, and together with alliteration and consonance serves as one of the building blocks of verse. For example, in the phrase "Do you like blue?", the is repeated within the sentence and is...

); but the term is sometimes used in these broader senses.