-τήρ

From Proto-Indo-European *-tḗr, with nominative η made common to all cases with original syncopation or ε; compare its use in ἀστήρ (astḗr) (always with ε) and γαστήρ (gastḗr) (either with oblique ε throughout or original syncopation).

-τήρ • (-tḗr) m (genitive -τῆρος, feminine -τειρᾰ); third declension

1. Added to verb stems to form masculine agent nouns

   ‎δίδωμι (dídōmi, “(δω-, weak stem δο- to give”) + ‎-τήρ (-tḗr) → ‎δωτήρ, δοτήρ (dōtḗr, dotḗr, “a giver”)

   ‎ἐργάζομαι (ergázomai, “to work”) + ‎-τήρ (-tḗr) → ‎ἐργαστήρ (ergastḗr, “workman”)

   ‎καθίημι (kathíēmi, “to let down, descend”) + ‎-τήρ (-tḗr) → ‎καθετήρ (kathetḗr, “anything let down into”)

   ‎κλύζω (klúzō, “to wash, cleanse”) + ‎-τήρ (-tḗr) → ‎κλυστήρ (klustḗr, “a clyster-pipe, syringe”)

   ‎ἵστημι (hístēmi, “(weak stem στα- to stand”) + ‎-τήρ (-tḗr) → ‎στατήρ (statḗr, “a weight”)

   ‎χαράσσω (kharássō, “(χαράκ-j- to engrave”) + ‎-τήρ (-tḗr) → ‎χαρακτήρ (kharaktḗr, “an engraver”)

• -τήριον (-tḗrion)
• -τήριος (-tḗrios)

• Greek: -τήρας (-tíras)

• -τής (-tḗs)
• -τωρ (-tōr)

• Smyth, Herbert Weir (1920), “Part III: Formation of Words”, in A Greek grammar for colleges, Cambridge: American Book Company, § 839.2