A reader recently inquired about the words wife and wives, particularly about the change in consonants between the singular wife and the plural wives. More broadly, why do some English nouns end in <f> or <fe> in the singular but <ves> in the plural?
Understanding plural forms like wives, knives, and leaves requires an understanding of Old English phonology, specifically knowledge of Old English allophones. Allophones are a set of speech sounds that represent a single phoneme. For example, consider the words ladder and latter. The <dd> in ladder can spell [d], and the <tt> in latter can spell [t]. However, in some Englishes, the alveolar flap [ɾ] is an allophone of both /d/ and /t/. Thus, for many English speakers, both ladder and latter sound the same, especially in natural speech.
As different phonetic realizations of the same phoneme, allophones are variations in sound that do not alter meaning. The pronunciation of ladder as [lædəɹ] or [læɾəɹ] and latter as [lætəɹ] or [læɾəɹ] does not change the meaning of either word. Both forms are valid and semantically identical.
In Old English, the fricative /f/ had two allophones: the voiceless [f] in word-final position and the voiced [v] between vowels or voiced consonants. Despite the difference in pronunciation, Old English used the same grapheme <f> in both contexts because [f] and [v] were allophones of /f/. Separate phonemes for [f] and [v] did not exist. Instead, both were context-driven realizations of the same underlying phoneme.
The Old English word for wife was wīf in the nominative form. The final <f> spelled the voiceless [f]: [wif]. In the genitive wīfa, which translates as wife’s, the medial <f> spelled the voiced [v]: [wivɑ].
This same phonological pattern occurred in other Old English nouns such as lēaf (nominative) and lēafa (genitive) meaning “leaf,” cnīf (nominative singular) and cnīfa/cnīfas (genitive/nominative plural) meaning “knife,” līf (nominative) and līfa (genitive) meaning “life,” healf (nominative) and healfa (genitive) meaning “half,” hlāf (nominative) and hlāfa (genitive) meaning “loaf,” þēof (nominative) and þēofa (genitive) meaning “thief,” and wulf (nominative) and wulfa (genitive) meaning “wolf.” In all these examples, the final <f> in the nominative form spelled the voiceless [f] while the medial <f> in the genitive or plural form spelled the voiced [v].
(Note: With the exception of cnīf~cnīfas, the plural forms of the other Old English nouns were identical to the singular forms, which reflects an inflectional pattern found in Old English neuter nouns. The term for this morphological invariance is zero inflection.)
During the Middle English period, [f] and [v] developed into separate phonemes rather than remaining allophones. Middle English wyf, wif had the plural forms wyfes, wyves, and wyve (among others because spelling had not yet been fixed). But, even though [f] and [v] were no longer allophones, using [f] word-final with wyf, wif and [v] medially with wyfes, wyves, wyve continued. Singular wyf, wif spelled [wif]. Plural wyfes, wyves, wyve spelled [wivəs] or [wivə].
When the spelling system was finally fixed by Modern English, both <Wife> and <Wive> developed as bases with <Wife> as the singular and <Wive> as an allomorph that forms the plural. The modern spellings reflect the pronunciations, which developed from Old English allophony.
<Wife → wife>
<Wive + s → wives>
The same is true for many other English nouns that end in <f> or <fe> in the singular and <ves> in the plural including leaf~leaves from Old English lēaf, knife~knives from Old English cnīf, life~lives from Old English līf, half~halves from Old English healf, loaf~loaves from Old English hlāf, thief~thieves from Old English þēof, and wolf~wolves from Old English wulf, among others.
The etymology of the words also explains the reason that not all nouns that end in <f> or <fe> have a different base in the plural. For example, Modern English chief comes from Old French chef, chief. The plural of chief is chiefs. Both the singular and plural have the same <Chief> base because, as a word from Old French, the Old English phonological rules did not apply. The <f> spelled [f] both word-final and medially.
Sometimes, speakers overextend the historical pattern governed by Old English phonological rules. The plural of dwarf was originally dwarfs. Then J.R.R. Tolkien popularized the plural form dwarves in his works. Now both dwarfs and dwarves are plural forms of dwarf. Conversely, historically governed plurals like hooves and wharves have also acquired the alternate forms hoofs and wharfs, which do not reflect allomorphic variation.
Long story short, the reason that some English nouns end in <f> or <fe> in the singular and <ves> in the plural is etymology and an understanding of Old English phonology, specifically Old English allophones.
