In this old document, the usage of vowels is different from today.

The nucleus is the central part of a syllable in phonetics.

Vowel harmony plays an important role in the phonology of certain languages.

There are five monophthongs in Japanese.

There are five short vowels in Japanese.

You need to be careful with the pronunciation of long vowels in Japanese.

A nasal vowel refers to a vowel that is pronounced through the nasal cavity.

A back vowel is a sound where the back of the tongue approaches the palate.

Back vowels are vowels that are pronounced using the back of the tongue.

A central vowel is a vowel that is pronounced in the central part of the tongue.