Usage: 3 forms in 10 verses
Form Translated As     In Verse(s)
έλοσ marsh LXX.Exod.2.3
έλη marshes LXX.Exod.8.5LXX.Isa.33.9LXX.Isa.35.7LXX.Isa.35.7LXX.Isa.41.18LXX.Isa.42.15
their marshes LXX.Exod.7.19
έλει marsh LXX.Exod.2.5LXX.Isa.19.6

Liddell-Scott-Jones

ἕλος (helos) a marsh TEGMC

ἕλος, εος, τό,

marsh-meadow, ἵπποι ἕλος κάτα βουκολέοντο [Refs 8th c.BC+]: generally, marshy ground, ἂν δόνακας καὶ ἕλος [Refs 8th c.BC+]

__2 backwater, δάσκιον . [Refs 3rd c.BC+]