ｓｙllable

I heard about syllable when I was a student. We can see words and syllables in dictionaries.
I haven't known English Haiku should have 5 syllables, 7 syllables and 5 syllables in one Haiku.
So I checked about syllable online. It says "音節（おんせつ）とは、シラブル（英語 syllable）ともいい、1個の母音を音節主音（おんせつしゅおん。英語 syllabic）とし、その母音単独で、あるいはその母音の前後に1個または複数個の子音を伴って構成する音声（群）で、音声の聞こえの一種のまとまりを言う。" in Japanese.
I also checked about Haiku. It says "Haiku (俳句, haikai verse?) listen (help·info), plural haiku, is a form of Japanese poetry, consisting of 17 moras (or on), in three metrical phrases of 5, 7, and 5 moras respectively.[1] Haiku typically contain a kigo, or seasonal reference, and a kireji or verbal caesura. In Japanese, haiku are traditionally printed in a single vertical line, while haiku in English usually appear in three lines, to parallel the three metrical phrases of Japanese haiku.[2] Previously called hokku, haiku was given its current name by the Japanese writer Masaoka Shiki at the end of the 19th century."

I wrote some Haiku in my last diary. I'll write one of them again.

I like Summer Holidays
very very much
being relaxed

It should have correct syllables.

I like Summer well
being relaxed and excited
during vacation

Actually counting syllables is difficult for me even though I can say these words correctly.