In half rhyme, the ending consonant sound of a word is the same as in the word with which it is intended to rhyme, but the final vowel sounds are not the same, such as in the words "sun" and "moon." For this reason, it is considered an imperfect rhyme. It also is called slant rhyme or oblique rhyme. The Icelandic, Irish, Scottish and Welsh are recognized as the first to use half rhyme, and it was a common feature in their classic poems. In English, half rhyme was first used by Henry Vaughan in the 1600s but did not become popular until it was used by poets such as Emily Dickinson, Gerard Manley Hopkins and Wilfred Owen in the 1800s or William Butler Yeats in the late 1800s and early 1900s.

Half rhyme applies only to words that have end consonant sounds that match, such as “cold” and “bald,” which is why it is considered a form of consonance. It is frequently confused with pararhyme and assonance. Both of these literary devices are similar to half rhyme, with only subtle differences. In the main feature of pararhyme, both the beginning and end consonants much have the same sound such as “red” and “rod.” When using assonance, only the vowel sounds match, as in “hot” and “bod.”