A Syllable is a unit of spoken language which typically consists of a vowel, optionally with a consonant before and/or after it. The number of letters in a syllable is not important as it is the sound of the syllable which matters.
One way to think of syllables is as beats of a song. For example, here’s a line from Happy Birthday:
Happy Birthday dear Annabel
And here it is broken down into syllables:
ha – ppy – birth – day – dear – ann – a – bel
From this you can see that a word like you is just 1 syllable or monosyllabic whereas a word like birthday has 2 syllables (or is disyllabic) and Annabel has 3 syllables (or is trisyllabic). A word with more than 3 syllables is polysyllabic.
The longest one-syllable word is scraunched which is found in a 1620 translation of Don Quixote. (It means to crunch or crackle.)
Teaching Using Syllables
Syllables can be thought of the building blocks of speech in the same way that letters are the building blocks of written language.
Suppose you are teaching a new word to your class; very possibly you’ll begin by saying the word clearly to your class both as a whole and also broken down into syllables, e.g.
dis – place – ment
Then you’ll write it up on the board. Syllables are often useful to use as a spelling aid; by breaking words down into syllables you can work out the spelling of each syllable and put them together to spell the word.
Another advantage of breaking it into syllables is that often syllables will form affixes; in the case of the word above the affixes and the root are obvious:
dis + place
place + ment
dis + place + ment
So by using syllables you can help your students with understanding, spelling and pronunciation.