A syllable is a part of a word that contains a vowel SOUND
Don’t confuse the vowel sounds with the number of vowels in a word. For example, heat contains two vowels, but only one vowel sound. It has only one syllable.
Create contains three vowels, but we only hear two, so it has two syllables (cre / ate).
It is important to know which syllable in a word is stressed. To stress the wrong syllable will make the word unintelligible or give it a different meaning. Some words change from nouns to verbs just by stressing a different syllable.
When you look up words in your English dictionary, be sure to check the stress in the word. It is just as important as the pronunciation of the letters.