How many vowels?

--To read this post in Japanese, click here.

I started to learn Arabic and found out that
Arabic has only three vowels.

Same goes with Inuit (spoken in Arctic regions),
and the Ryukyuan language  (spoken in Japan).
(There is a dispute whether the Ryukyuan is
an independent language or a dialect of Japanese.)

Ubykh, which is an extinct language spoken near the Black Sea,
had only two vowels.

English: vowel

French: voyelle

Italian: vocale

Spanish: vocal

German: Vokal

Japanese: 母音 [boin]

Korean: 모음 [moum]

Chinese: 元音 [yuanin]

Dutch: klinker

Arabic: [harafalyin] حرف لين