The difference between alliteration and assonance in the English language is that alliteration is the complementary use of identical consonants at the beginning of words, where assonance is the use of complementary identical vowel sounds within a word. These two ideas are ubiquitous in some sorts of poetry and prose, especially in classic eras, where writers used them quite liberally for dramatic effect. These two literary conventions are technically different, though they may function in much the same way.
In addition to alliteration and assonance, it’s important to recognize another similar element called consonance. Consonance is the agreement or use of identical consonants in any parts of a word, where alliteration is specifically the use of identical consonants at the beginnings of words. Thus, alliteration is the only member of the three that is tied exclusively to the beginning of words. These terms represent very similar ideas, though each is technically distinct; consequently, it is common for them be confused in conversation.
One of the most primary uses of alliteration comes from a long history of use within the English language. Ancient forms of English, such as Old English, use alliteration prolifically. Other languages like Old Norse and Saxon used alliteration as well, where the correspondence of consonant sounds held a certain power for the respective linguistic communities.
Another difference between alliteration and assonance is in the unique types of sounds that these methods bring to a sentence or phrase. Alliteration is something that in modern times is useful in special phrases called “tongue twisters.” For example, the phrase “Sally sold sea shells by the sea shore” uses a kind of staggered alliteration, vacillating between the initial “s” sound and the “sh” sound, to show children how to differentiate between these two consonants. Alliteration may also be useful in other items called mnemonic devices, where individuals think up their own “catch phrases” to remember complex bundles of words for security passwords or other purposes.
By contrast, assonance is used more to display the unique vowel sounds that are present in the English language. For example, if someone says “Don’t break your stake,” they may be demonstrating how diverse groups of letters form the same “long a” vowel sound. This gives beginners more of an idea of how a given vowel sound is represented in different ways on paper to represent different meanings. Alliteration and assonance can therefore both be used as effective tools in teaching various elements of pronunciation and spelling.