Consonants and vowels correspond to distinct parts of a syllable: The most sonorous part of the syllable (that is, the part that's easiest to sing), called the "syllabic peak" or "nucleus," is typically a vowel, while the less sonorous margins (called the "onset" and "coda") are typically consonants. Such syllables may be abbreviated CV, V, and CVC, where C stands for consonant and V stands for vowel. This can be argued to be the only pattern found in most of the world's languages, and perhaps the primary pattern in all of them. However, the distinction between consonant and vowel is not always clear cut: there are syllabic consonants and non-syllabic vowels in many of the world's languages.