Assonance is defined as "a resemblance in the sounds of words or syllables, either between their vowels (e.g. meat, bean) or between their consonants (e.g. keep, cape)". This latter kind, in which the consonants remain the same but the vowel changes, in American usage is generally called consonance. Often the two types are combined, as between the words six and switch, in which the vowels are identical, and the consonants are similar but not completely identical.
Rhyme, in which the final stressed syllables of words differ in their initial consonant while the rest of the word is identical, as in six and mix, or history and mystery, is a special case of assonance.
A concise, tongue-in-cheek summing up of assonance is given by Rita, the eponymous character of Educating Rita, i.e. assonance is getting the rhyme wrong.
English poetry is rich with examples of assonance:
That solitude which suits abstruser musings
on a proud round cloud in white high night-- E. E. Cummings, if a cheerfulest Elephantangelchild should sit
It also occurs in prose:
Soft language issued from their spitless lips as they swished in low circles round and round the field, winding hither and thither through the weeds.
Senator, in everything I said about Iraq I turned out to be right and you turned out to be wrong.
Some vodka that'll jumpstart my heart quicker than a shock when I get shocked at the hospital by the doctor when I'm not cooperating...
Dead in the middle of little Italy little did we know that we riddled some middleman who didn't do diddly.-- Big Pun, Twinz
Can't tell me shit about the tricks of this trade
Switchblade, with a little switch to switch blades
And switch from a six to a sixteen-inch blade-- Eminem, "Rap Game"
It is also heard in other forms of popular music:
I must confess that in my quest I felt depressed and restless-- Thin Lizzy, "With Love"
Dot my I's with eyebrow pencils, close my eyelids, hide my eyes. I'll be idle in my ideals. Think of nothing else but I-- Keaton Henson, "Small Hands"
Assonance is common in proverbs, such as:
The squeaky wheel gets the grease.
The early bird catches the worm.
These proverbs can be a form of short poetry, as in the following Oromo proverb, which describes someone with a big reputation among those who do not know them well:
kan mana baala, a?laa gaala (A leaf at home, but a camel elsewhere)
Note the complete assonance in this Amharic proverb:
yälämmänä mänämmänä (The one who begs fades away)