unrealizable

Etymology tree
Proto-Indo-European *né
Proto-Indo-European *n̥-
Proto-Germanic *un-
Proto-West Germanic *un-
Old English un-
Middle English un-
English un-
Proto-Indo-European *(H)reh₁-der.
Proto-Indo-European *(H)reh₁ís
Proto-Italic *reis
Latin rēs
Proto-Indo-European *h₂el-der.?
Proto-Italic *-ālis
Late Latin -ālis
Late Latin reālisder.
Old French reelbor.
Middle English real
English real
Proto-Indo-European *-id-
Proto-Indo-European *-yéti
Proto-Indo-European *-idyéti
Proto-Hellenic *-íďďō
Ancient Greek -ῐ́ζω (-ĭ́zō)bor.
Late Latin -izōder.
Middle French -iserbor.
Middle English -isen
English -ize
English realize
Proto-Indo-European *-tḗr
Proto-Indo-European *-dʰlom
Proto-Indo-European *-dʰlis
Proto-Italic *-ðlis
Latin -bilis
Latin -ābilis
Old French -ablebor.
Middle English -able
English -able
English realizable
English unrealizable
From un- + realizable.