A syllable is a unit of sound that is typically produced with a single pulse of air from the lungs. It is a single, unbroken sound of a spoken (or written) word, usually containing a vowel and accompanying consonants. Syllables are often considered the phonological "building blocks" of words and can influence the rhythm of a language, its prosody, its poetic meter, and its stress patterns.
To identify syllables, one can think about whether they need to change their mouth shape to say the next bit of the word or the new syllable. The number of times a vowel (a, e, i, o, u) is heard in a word is equal to the number of syllables the word has. Teachers often get children to clap out the syllables of a word to help them understand the concept.
Syllables are important in learning how to decode and spell words, as they help children understand the conventions of English spelling, including when to double letters and how to pronounce the vowels in words they might not have seen before.