noun
syllabic
Technical term in phonetics referring to a sound that functions as the nucleus of a syllable.
日本語では、母音が音節主音になることが多い。
In Japanese, vowels often become the syllabic nucleus.
音節 means 'syllable', while 音節主音 specifically refers to the syllabic element (nucleus) within a syllable.
Compound of 音節 (syllable) and 主音 (principal sound), likely a calque from Western linguistic terminology.