A syllable is a part of a word pronounced as a unit. It is usually made up of a vowel alone or a vowel with one or more consonants. The word "Haiku" has two syllables: Hai-ku; the word "introduction" has four syllables: in-tro-duc-tion.
"Haiku" is a traditional form of Japanese poetry. Haiku poems consist of 3 lines. The first and last lines of a Haiku have 5 syllables and the middle line has 7 syllables. The lines rarely rhyme.