A syllable (音节) is made up of one or more letters with a vowel(元音) sound at its core.

This does not necessarily mean that every syllable contains a vowel, but it will include a vowel sound when pronounced.

1 vowel sound:

cat
dog
all
at
go

2 vowel sounds:

turtle
purple
forest
frozen
bingo
tiger

3 vowel sounds:

computer
employee
generate
medecine