Proto-Finnic/Phonology

Consonants

		Labial	Dental/Alveolar	Palatal	Velar
Nasals		/m/ ⟨m⟩	/n/ ⟨n⟩
Plosives	Voiceless	/p/ ⟨p⟩	/t/ ⟨t⟩		/k/ ⟨k⟩
Plosives	Voiced	/b/ ⟨b⟩	/d/ ⟨d⟩		/ɡ/ ⟨g⟩
Affricate			/t͡s/ ⟨c⟩
Fricatives			/s/ ⟨s⟩		/x/ ⟨h⟩
Trill			/r/ ⟨r⟩
Approximant		/ʋ/ ⟨v⟩		/j/ ⟨j⟩
Lateral			/l/ ⟨l⟩

All consonants except /b, d, ɡ, h, j, ʋ/, can be geminated. The geminated obstruents *cc, *kk, *pp, and *tt are subject to consonant gradation into half-long obstruents *c', *k', *p', and *t', respectively (see more at § Morphophonology). The voiced plosives are pronounced as fricatives [β, ð, ɣ] when following vowels and /l, r/, although the voiced plosives only fully merged with fricatives as suggested by assimilation into nasals in some languages ([mb, nd, ŋɡ] → [mβ, nð, ŋɣ] → Finnish mm, nn, ng /mː, nː, ŋː/). It is important to note that Estonian lacks phonemic /ŋ/, so the allophony are still preserved in some dialects.

Vowels

	Front		Back
	Unrounded	Rounded	Unrounded	Rounded
Close	/i/, /iː/ ⟨i⟩, ⟨ii⟩	/y/, /yː/ ⟨ü⟩, ⟨üü⟩		/u/, /uː/ ⟨u⟩, ⟨uu⟩
Mid	/e/, /eː/ ⟨e⟩, ⟨ee⟩	/ø/, /øː/ ⟨ö⟩, ⟨öö⟩	(/ɤ/, /ɤː/) (⟨ë⟩, ⟨ëë⟩)	/o/, /oː/ ⟨o⟩, ⟨oo⟩
Open	/æ/, /æː/ ⟨ä⟩, ⟨ää⟩		/ɑ/, /ɑː/ ⟨a⟩, ⟨aa⟩

There are also phonemes /ɤ/, /ɤː/ (written as ⟨ë⟩, ⟨ëë⟩ in Proto-Finnic contexts) in Southern Finnic, usually results from rounding of *e in back harmony words (*velka → *vëlka → Estonian *võlg), but also from other sporadic changes such as Southern Proto-Finnic *sëna : Northern Proto-Finnic *sana, SPF *hëbëda : NPF *hobeda, and SPF *mëistadak : NPF *muistadak. Because of this, some preferred to reconstruct words with *ë, at least dialectally (Southern Proto-Finnic).

Morphophonology

Vowel harmony

Vowel harmony is a feature occurring in many Finnic languages, notable exceptions include (North) Estonian and Livonian. Proto-Finnic morphologically distinguished back vowels *a, *ë (in some dialects), *u, front vowels *ä, *e, *ö, *ü, and neutral vowels *i, *o. The vowel ö is always followed by front vowels, but o usually followed by back and neutral vowels, but can be preceded by all vowels.

Consonant gradation

Consonant gradation is a feature occurring in almost all Finnic languages, except Livonian, Ludic, and Veps. There are originally two types of consonant gradation:

Radical gradation: Occurring in non-initial closed syllables. This causes strong grade consonants become weak.

Strong grade	Weak grade
*cc	*c'
*k	*g
*kk	*k'
*p	*b
*pp	*p'
*t	*d
*tt	*t'

Radical gradation is restricted after vowels, sonorants (*l, *m, *n, *r), and homorganic stops, although it later extended to *h, *k albeit inconsistently. Gradated syllables also influenced preceding syllable's long vowel (*kee·li : *kee·len → *keeeli : *keelen → keel : keele /ˈkeːːl : ˈkeːle/ "tongue") in Estonian.

Note that *s → *h gradation is sporadic; and it largely occurs in s-stem nouns (nominative *pensas → genitive *pensahen "brush"), illative *-sen ~ *-hen, connegative past *-(t)tisen ~ *-(t)tihen. It also occurred on the irregular noun *mees → genitive *meehen "man" (but maa → illative *maasen) All of the former examples are subject to suffixal gradation.

Suffixal gradation: Occurring in non-initial odd-numbered syllables. It is now less productive than radical gradation in modern languages, although it leaves some remnants such as the Finnish partitive suffix -ta changes -a after short vowels, otherwise -ta.

Strong grade	Weak grade
*k	*g
*p	*b
*t	*d

Suffixal gradation is restricted into intervocalic positions.

Examples

	"tree"	"hut"	"cover"	"blind"
Nominative	*puu	*ko·ta	jä·t'ek*	*so·ke·da
Genitive	*puun	ko·dan*	jä·tte·gen*	so·ke·dan*
Partitive	*puu·ta	*ko·ta·da	jä·t'ek*·tä	*so·ke·da·ta
Illative	*puu·sen	ko·ta·hen*	*jä·tte·ge·sen	*so·ke·da·sen
Inessive	*puus·sa	ko·das*·sa	jä·tte·ges*·sä	so·ke·das*·sa