Cases in -φι (ν).—-φι (ν) is often added to noun stems in Hom. to express the relations of the lost instrumental, locative, and ablative, both singular and (more commonly) plural; rarely to express the relations of the genitive and dative cases. From α_ stems are made singulars, from ο stems singulars or plurals, from consonant stems almost always plurals. Except in θεό-φιν
Herbert Weir Smyth [n.d.], A Greek Grammar for Colleges; Machine readable text [info] [word count] [Smyth].