-σις

See also: Appendix:Variations of "sis"

Ancient Greek

From earlier -τις (-tis) (retained after dentals), from Proto-Indo-European *-tis. The *t changed to *s by assibilation and palatalization, triggered by the following *i. Cognates include Latin -tiō.

-σῐς • (-sis) f (genitive -σεως or -σῐος or -σηος); third declension

Added to verb stems to form abstract nouns or nouns of action, process, or result

Case / #	Singular	Dual	Plural
Nominative	-σῐς -sis	-σει -sei	-σεις -seis
Genitive	-σεως -seōs	-σέοιν -séoin	-σεων -seōn
Dative	-σει -sei	-σέοιν -séoin	-σεσῐ / -σεσῐν -sesi(n)
Accusative	-σῐν -sin	-σει -sei	-σεις -seis
Vocative	-σῐ -si	-σει -sei	-σεις -seis
Notes:	This table gives Attic inflectional endings. For declension in other dialects, see Appendix:Ancient Greek dialectal declension.

Case / #	Singular	Dual	Plural
Nominative	-σῐς -sis	-σῐε -sie	-σῐες -sies
Genitive	-σῐος -sios	-σῐ́οιν -síoin	-σῐ́ων -síōn
Dative	-σῑ -sī	-σῐ́οιν -síoin	-σῐσῐ / -σῐσῐν -sisi(n)
Accusative	-σῐν -sin	-σῐε -sie	-σῑς / -σῐᾰς -sīs / -sias
Vocative	-σῐ -si	-σῐε -sie	-σῐες -sies
Notes:	Dialects other than Attic are not well attested. Some forms may be based on conjecture. Use with caution.

Case / #	Singular	Dual	Plural
Nominative	-σῐς -sis	-σῐε -sie	-σῐες / -σηες -sies / -sēes
Genitive	-σῐος / -σηος -sios / -sēos	-σῐ́οιῐν -síoiin	-σῐ́ων -síōn
Dative	-σῐῐ / -σῑ / -σηῐ̈ / -σει -sii / -sī / -sēï / -sei	-σῐ́οιῐν -síoiin	-σῐ́εσσῐ / -σῐ́εσσῐν / -σεσῐ / -σεσῐν / -σῐσῐ / -σῐσῐν -síessi(n) / -sesi(n) / -sisi(n)
Accusative	-σῐν -sin	-σῐε -sie	-σῐᾰς / -σηᾰς / -σῑς -sias / -sēas / -sīs
Vocative	-σῐ -si	-σῐε -sie	-σῐες / -σηες -sies / -sēes
Notes:	Dialects other than Attic are not well attested. Some forms may be based on conjecture. Use with caution.

Smyth, Herbert Weir (1920) “Part III: Formation of Words”, in A Greek grammar for colleges, Cambridge: American Book Company, § 840.2