The phenomenon of off-rhyming is based upon the relationship of similarity among sounds. Sounds perceived as like one another create acceptable off-rhyming pairs. Because the distinctive features of sounds are hierarchically arranged in languages, off-rhyming patterns can reveal the groupings within these hierarchies. Changes in pattern diachronically or among synchronic dialects express rearrangements in the phonological structure of the language. With respect to the consonantal features of English, off-rhymes in the codas of rhyming syllables in the works of twenty British poets writing from c. 1600–1900 have been examined to discover acceptable patterns of similarity. Most common are rhymes of voiceless and voiced pairs of homorganic consonants; /s/ to /z/ is the most frequent pair. The most frequent rhymes apart from homorganic pairs involve alveolar and alveopalatal consonants. With respect to acoustic features, the most frequent rhymes utilize the [±tense] feature, then [±compact] (with [±strident] playing a minor role). These patterns remain consistent over time and across dialects.