-ης

From Proto-Indo-European *-ēs, from masculine *-s over *-os ~ -es- neuter substantive nouns. Afterwards used freely.

-ης • (-ēs) m or f (neuter -ες); third declension

1. Forms third-declension adjectives with stems in -εσ- (-es-); very common in compounds.

   ‎γένος (génos, “offspring, kind”) + ‎-ης (-ēs) → ‎-γενής (-genḗs, “genes”)

   ‎εἶδος (eîdos, “form, appearance”) + ‎-ης (-ēs) → ‎-ειδής (-eidḗs, “-eides”)

   ‎κλέος (kléos, “fame, glory”) + ‎-ης (-ēs) → ‎-κλεής (-kleḗs, “-klees”) → -κλής (-klḗs)

   ‎κρᾰ́τος (krátos, “might”) + ‎-ης (-ēs) → ‎-κρᾰτής (-kratḗs, “-crates”)

   ‎ἀ- (a-) + ‎ληθ- (lēth-) + ‎-ης (-ēs) → ‎ᾰ̓ληθής (alēthḗs)

   ‎μένος (ménos, “might”) + ‎-ης (-ēs) → ‎-μενής (-menḗs, “-menes”)

   ‎πλῆθος (plêthos, “multitude”) + ‎-ης (-ēs) → ‎-πληθής (-plēthḗs, “-plethes”)

   ‎σθένος (sthénos, “strength”) + ‎-ης (-ēs) → ‎-σθενής (-sthenḗs, “-sthenes”)

   ‎φᾰ́ος (pháos, “light”) + ‎-ης (-ēs) → ‎-φαής (-phaḗs, “-phaes”)

-ης • (-ēs) m (genitive -ους or -εος); third declension

1. Forms third-declension proper nouns.

   ‎κλέος (kléos, “fame, glory”) + ‎-ης (-ēs) → ‎-κλέης (-kléēs, “-klees”) → -κλῆς (-klês)

   ‎κρᾰ́τος (krátos, “might”) + ‎-ης (-ēs) → ‎Κρᾰ́της (Krátēs), -κρᾰ́της (-krátēs)

   ‎μένος (ménos, “might”) + ‎-ης (-ēs) → ‎-μένης (-ménēs, “-menes”)

   ‎σθένος (sthénos, “strength”) + ‎-ης (-ēs) → ‎-σθένης (-sthénēs, “-sthenes”)

• Sihler, Andrew L. (1995) New Comparative Grammar of Greek and Latin, Oxford, New York: Oxford University Press, →ISBN
• Smyth, Herbert Weir (1920) “Part III: Formation of Words”, in A Greek grammar for colleges, Cambridge: American Book Company, § 858.5

• IPA^(key): /is/

-ης • (-is) (ending of masculine nouns)

1. ending of parisyllabic masculine nouns, deriving from ancient 1st declension
   1. in -ης, -η, plural -ες, -ών, e.g. ναύτης (náftis, “sailor”) < ναύτης
   2. in -ής, -ή, plural -ές, -ών, e.g. μαθητής (mathitís, “student”) < μαθητής
2. ending of parisyllabic masculine nouns deriving from ancient 3rd declension
   1. in -ης, -η, plural -εις, -εων e.g. λάτρης (látris, “worshipper”) < λάτρις (“servant -of god”), μάντης (mántis, “seer”) < μάντις, πρύτανης (prýtanis, “rector”) < πρύτανις (“ruler”)
3. ending of imparisyllabic masculine nouns deriving from ancient -ιος, -ειος
   1. in -ης, plural -ηδες e.g. κύρης (kýris, “master”) < κύριος, Βασίλης (Vasílis, “Basel”) < Βασίλειος
   2. in -ής, plural -ήδες (rare) e.g. πεταλωτής (petalotís, “farrier”) < πεταλώνω from Hellenistic πεταλῶ < ancient πέταλον
4. ending of imparisyllabic masculine nouns borrowed from Turkish -cı.
   1. in -τζής plural -τζήδες e.g. καφετζής (kafetzís, “café owner or waiter”) < Turkish kahveci

-ης • (-is) (ending of adjectives)

1. ending of formal adjectives in -ης, -ης, -ες or -ής, -ής, -ές deriving from the corresponding ancient 3rd declension

   e.g. πλήρης (plíris, “full”) < πλήρης, αήθης (aḯthis, “immoral”) < ἀήθης

2. ending of adjectives in -ης, -α, -ικο deriving from Medieval Greek

   e.g. ζηλιάρης (ziliáris, “jealous”)

3. ending of adjectives in -άρης (-áris) plural -άρηδες borrowed from Latin -ārius.

   e.g. ταβερνιάρης (taverniáris, “taverna owner”)

4. ending of adjectives in -ής, -ιά, -ί and indeclinable -ί, borrowed from Turkish -i (-ι, -u, -ü) mainly for names of colours

   e.g. καφετής (kafetís, “brownish”)

-ης • (-is) f (inflectional feminine form)

1. genitive singular ending of feminine nouns and adjectives ending in -η deriving from ancient genitive -ης or -ῆς

   e.g. της φίλης f (fílis, “friend (female)”) < τῆς φίλης

   e.g. της μουσικής f (mousikís, “music”) < τῆς μουσικῆς

-ης • (-is) (ending of adverbs)

1. adverbs in -ής deriving from genitive feminine ending, Hellenistic or Medieval -ῆς.

   e.g. επικεφαλής (epikefalís, “in charge”), καταγής (katagís, “down on the ground”)

-ης • (-is) (obsolete inflectional verb ending)

1. ending of 2nd person, singular, subjunctive used until the 1960s, deriving from its ancient -ῃς (-ēis) equivalent

   να λύνεις (na lýneis, “to untie, solve”), or λύεις < να λύνης < ἵνα λύῃς

The dated subjunctive endings -ης^{2nd singular}, -η^{3rd singular}, -ωμεν^{1st plural} may be found in grammar books for Modern Greek published before 1976, when they were reedited to the identically-pronounced indicative endings -εις, -ει, -ουμε/-ομε as Demotic Greek became the official language of education in Greece.

• "-ης" - Λεξικό της κοινής νεοελληνικής [Dictionary of Standard Modern Greek], 1998, by the "Triantafyllidis" Foundation.