Phoneme hole

A phoneme hole is a feature of a language's phonology, where an 'expected' phoneme does not occur. What counts as 'expected' is debatable, but at a pinch, a language would be expected to cover as many combinations of its allowed place of articulation and manner of articulation as possible.

An example of a consonant inventory without holes might be:

p	t	k
b	d	g
f	s	x
v	z	ɣ
m	n	ŋ

while one with several holes might be:

	t	ʈ	k
b		ɖ
f	s		x
m	n	ɳ
ʋ		ɭ	ɣ

The 6 'missing' phonemes would be **/p, d, g, ʂ, ŋ, l/.

History

Phoneme holes may arise in at least three basic ways:

• A previous phoneme has changed into another sound, leaving its place vacant. In example II, possibly *p → f.
• A phoneme class has arisen in a way that does not allow all possible combinations to arise (perhaps reproducing a hole in another part of the phonology). In example II, possibly *ʋ, *ɭ → b, ɖ under certain conditions; since no alveolar (lateral) approximant **l exists, no **d will exist either.
• A hole has persisted as long as a language's history is traceable. In example II, possibly no **ŋ ever existed.

"Wide" phonemes

A separate phenomenon from phoneme holes is a lack of distinction between certain POA/MOA combinations. A phoneme of this type may be realized intermediate to, or varying between the 'expected' values. In example II, possibly /ɣ/ has an allophone [g] under certain conditions, which would mean that the /g/ slot is not truly vacant.

Typical examples:

• The open vowel /a/ is in most languages not subject to the front/back contrast distinguishing /i/ and /u/, or /e/ and /o/. Its realization in any individual language may vary from front [a] to central [ä] to back [ɑ].
• The labial-velar approximant /w/ in most languages contrasts neither with a bilabial approximant nor a velar approximant. In many cases, a more economic analysis than considering it a language's only consonant at the labiovelar place of articulation, is to consider it as simultaneously occypying the labial and the velar POAs.

Common one-phoneme holes

• Implosives: lack of the velar implosive /ɠ/
• Nasals: lack of the velar nasal /ŋ/ or the palatal nasal /ɲ/ (occasionally both)
• Stops: lack of the voiced velar stop /g/ (commonly due to lenition)
• Stops: lack of the voiceless bilabial stop /p/ (commonly due to a shift to /ɸ/ → /f/ or /h/)

Impossible phonemes

Certain POA/MOA combinations are necessarily lacking from human languages due to articulatory constraints. These include, among others:

• Labial laterals
• Glottal nasals
• Voiced glottal stop