Back Vowel

Definition:

A back vowel is a vowel sound produced with the highest point of the tongue retracted toward the back of the oral cavity, near the velum (soft palate). On the IPA vowel chart, back vowels occupy the right column. Common examples include /u/ (as in “food”), /o/ (as in “go”), and /ɑ/ (as in “father”).

In-Depth Explanation

Back vowels are characterized by tongue retraction and typically have lower second formant frequencies (F2) than front vowels, giving them a “darker” or “rounder” quality. Most back vowels are rounded (produced with lip rounding), though unrounded back vowels exist.

Back vowels in Japanese:

Japanese has two back vowels:

• /ɯ/ — A close back unrounded vowel. This is the Japanese う sound. Crucially, it is unrounded — the lips do not protrude or round. English /u/ (“food”) is rounded, and substituting it sounds noticeably foreign. Additionally, Japanese /ɯ/ is somewhat centralized, making it phonetically between a true back vowel and a central vowel.
• /o/ — A mid back rounded vowel. Similar to Spanish /o/ or the first part of English “go,” but without the diphthongal glide to /ʊ/ that English “go” (/goʊ/) typically has. Like all Japanese vowels, /o/ is a pure monophthong.

The /ɯ/ distinction is one of the subtler but important pronunciation points for English speakers learning Japanese. It’s especially noticeable in common words like です (desu) and ます (masu), where the final /ɯ/ is often devoiced (produced without voicing, becoming barely audible) — not produced as a full English “oo.”

Related Terms

• Front Vowel
• Central Vowel
• Rounded Vowel
• Unrounded Vowel
• Close Vowel

See Also

• Japanese Phonology
• Sakubo

Research

• Ladefoged, P., & Johnson, K. (2014). A Course in Phonetics (7th ed.). Cengage Learning. — Standard vowel classification reference with acoustic data for back vowels.
• Okada, H. (1991). Japanese. Journal of the International Phonetic Association, 21(2), 94–97. — IPA description of Japanese vowels including the centralized nature of /ɯ/.