Here's why:
* It names a thing: Syllables are the units of pronunciation that make up a word.
* It can be the subject of a sentence: "Syllables" can be the subject of a sentence, as in "Syllables are important for pronunciation."
* It can be modified by adjectives: You can describe syllables with adjectives, such as "stressed syllables" or "unstressed syllables."
Let me know if you'd like more examples!