Syllable - Wikipedia

Words consist of syllables. Each syllables consists of "margins" (edges) and a "nucleus" (middle). Vowel sounds occur in the nucleus of a syllable; consonant sounds occur in the margins. In English, syllables can begin or end with consonants or vowels. Other languages sometimes insist that every syllable end in a vowel or begin with a consonant. On the other hand, no known language insists that syllables begin with a vowel or end in a consonant.

In linguistics jargon, basic syllable structure is often listed using abbreviations, where C represents any consonant and V any vowel, for instance:

CV - beginning consonant, vowel
CV(C) - beginning consonant, vowel, optional closing consonant

See phonetics.