Usage: 2 forms in 2 verses
Form Translated As     In Verse(s)
διαφωτίση it should illuminate LXX.1Sam.14.36
διαφωτίσαι illuminating LXX.Neh.8.3

Liddell-Scott-Jones

διαφωτίζω (diaphōtizō) to illuminate G:V

διαφωτίζω-ίζω,

enlighten, τὴν ψυχήν [Refs 1st c.AD+]; βίᾳ διαφωτίζωίσαι τόπον clear a place by force, [Refs]; throw light upon, νυκτερινὰς διατριβάς [Refs 2nd c.AD+]: absolutely, dawn, [LXX]

LSJ Scripture Refs: LXX.Neh.8.3