From Rhymes With Orange, playing with morphophonology: Some English nouns ending in voiceless fricatives (especially in /f/) voice these fricatives in the plural. There are three classes of cases: (1) voicing obligatory in standard English: wife – wives, shelf – shelves; (2) voicing variable in standard English: wharf – wharves/wharfs, dwarf – dwarves/dwarfs (see the … Continue reading Arf