A syllable is a basic unit of organization within a sequence of speech sounds, such as within a word, typically defined by linguists as a nucleus (most often a vowel) with optional sounds before or after that nucleus (margins, which are most often consonants). In phonology and studies of languages, syllables are often considered the "building blocks" of words. They can influence the rhythm of a language: its prosody or poetic metre. Properties such as stress, tone, and reduplication operate on syllables and their parts. Speech can usually be divided up into a whole number of syllables: for example, the word ignite is made of two syllables: ig and nite. Most languages of the world use relatively simple syllable structures that often alternate between vowels and consonants.
Despite being present in virtually all human languages, syllables still have no precise definition that is valid for all known languages. A common criterion for finding syllable boundaries is native-speaker intuition, but individuals sometimes disagree on them.