Usage: 8 forms in 26 verses
Form Translated As     In Verse(s)
πρόθυρόν my threshold LXX.Ezek.43.8
πρόθυρον threshold LXX.Gen.19.6LXX.Judg.19.27LXX.1Sam.5.4
πρόθυρα thresholds LXX.1Kgs.7.50LXX.2Kgs.12.9LXX.1Chr.9.19LXX.Jer.1.15LXX.Ezek.8.3LXX.Ezek.8.7LXX.Ezek.8.14LXX.Ezek.10.19LXX.Ezek.46.2LXX.Ezek.46.3LXX.Ezek.47.1LXX.Zech.12.2
προθύρων threshold LXX.Ezek.11.1
thresholds LXX.Jer.19.2LXX.Ezek.8.16
προθύρω threshold LXX.1Kgs.14.17
προθύρου threshold LXX.Ezek.46.2
προθύροισ αυτών their thresholds LXX.Ezek.43.8
προθύροισ thresholds LXX.Isa.66.17LXX.Jer.26.10LXX.Jer.36.10LXX.Jer.43.9

Liddell-Scott-Jones

πρόθυρον (prothuron) a threshold G:N-N

πρόθυρον-ον, τό,

front-door, door-way, especially of the entrance to the αὐλή, ἐκ δ᾽ ἔλασε προθύροιο καὶ αἰθούσης [πρόθυρονα δωμάτων 4th-5th c.BC: Aeschylus Tragicus “Choephori” 966 (Lyric poetry), compare 5th c.BC: Euripides Tragicus “Troades” 194 (Lyric poetry) ">Refs 8th c.BC+]; of the entrance to the μέγαρον, [Refs 8th c.BC+]

__2 porch, portico, παραστάδας καὶ π. βούλει ποικίλα [Refs 5th c.BC+]
__3 space before a door, whether or not it is a porch or portico: before the outmost entrance, plural, [Refs 8th c.BC+]; before the entrance of a νεωκόριον, [Refs]
__II metaphorically, Κόρινθος Ἰσθμίου πρόθυρονον Ποτειδᾶνος [πρόθυρονα καὶ σχῆμα.. σκιαγραφίαν ἀρετῆς περιγραπτέον [prev. author] “R.” 365c; χείλη.. στόματος νεκταρέου πρόθυρονα “Anthologia Graeca” 5.55 (3rd c.BC: Dioscorides Epigrammaticus). ">Refs 5th c.BC+]