θνήσκω The Root is ΘΑΝ, found in aor2 θανεῖν, etc. The form τεθνειώς appears as a variant reading at Iliad 17.161
I.to die, be dying, in aor2 and perf. to be dead, Hom., etc.; the pres. sometimes takes a perf. sense, θνήσκουσι γάρ, for τεθνήκασι, Soph., Eur.
2.often used like a pass. Verb, χερσὶν ὑπ᾽ Αἴαντος θανέειν to fall by his hand, be slain by him, Il., etc.:—note the phrase of Dem., τεθνᾶσι τῶι δέει τοὺς τοιούτους, where τεθνᾶσι τῶι δέει must be taken as a single Verb, are in mortal fear of.
II.metaph. of things, to die, perish, Aesch., Soph., etc.