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.”
A poet might use half rhyme for several reasons. As with some other poetic devices, it forces the reader to take pause and notice the difference in the words. Sometimes it even makes the reader re-read the passage to figure out why the poem sounds “off.” This is because half rhyme is usually used with other poetic devices, making the reader form expectation. When the slant rhyme is used, it breaks that expectation and essentially shocks the senses.
The sometimes harsh and off-key nature of this rhyming method is occasionally applied to fit the mood of the poem. Quirky and off-beat poems do well with type of rhyme as a main feature. Poems that represent a character’s thought or quote might also use half rhyme because it flows more like natural conversation, given that it is not typical for a person to think or speak in perfect rhyme.
Using this rhyming method also gives a poet more creative freedom. It allows a poet to match a word with another when there is no actual rhyme available. This use of creative license is commonly used by modern poets and rap musicians.