Onsets and rimes are parts of syllables or monosyllabic words in spoken language. These units are smaller than syllables but may be larger than phonemes. An onset is the initial consonant sound of a syllable (the onset of bag is b-; of swim is sw-). The rime is the part of a syllable that contains the vowel and all that follows it (the rime of bag is -ag; of swim is -im).