Usage: 2 forms in 2 verses
Form Translated As     In Verse(s)
σύννυμφόσ sister-in-law LXX.Ruth.1.15
συννύμφησ your sister-in-law LXX.Ruth.1.15

Liddell-Scott-Jones

σύννυμφος (sunnumphos) a sister-in-law G:N-F

σύννυμφος, ,

husband's brother's wife, [LXX+2nd c.AD+]

LSJ Scripture Refs: LXX.Ruth.1.15