I’ve been thinking a bit lately about pluralisation. There are many languages, like Mandarin or Japanese, in which nothing pluralises; there are languages where words generally pluralise in only one way, like in English; and there are ones which have a whole range of pluralisation patterns, like Latin.
But what I’ve been wondering is: do all natural pluralising languages have some words which don’t have a distinct plural form? And why?
For instance, Latin félés (cat) doesn’t change from nominative (or vocative) singular to plural. In this case, we know that there was a coexistent spelling félis, which became félés in the plural. So we can speculate that some speakers began to use the plural form as the singular, similar to what’s happening now with English data eclipsing the original singular datum.
English fruit is a loanword from Old French, in which it also had no distinct plural form in the nominative. Its ancestor, Latin fructus pluralised to fructús, only lengthening the final vowel; this lengthening could easily have been lost in the transition to French, or in Late Latin, or perhaps was non-existent in Vulgar Latin since an unknown time. Manuscripts and inscriptions written without apices (aka. accents marking long vowels) wouldn’t have recorded the plural distinction, giving further momentum to the change.
Other words like sheep, bread, and fish are Germanic in origin, and as such we can’t explore their etymology before Old English. The word brēad had a nominative plural brēadru; fisċ had a plural fiscas. But without properly researching the subject, I can’t say whether these were used as “true plurals” or instead to refer to different types of bread and fish like today. The reason for squid and shrimp not pluralising may be due to analogy with fish; and in turn, the reason for fish not modifying as a plural could be because they were often caught in nets as groups.
Sċēap (sheep) appears never to have had a plural morph in recorded English. However, German Schaf becomes plural Schafe, and Dutch schaap becomes plural schapen. The English words for other herding animals like cows and goats kept their plurals – the reason why we cannot today say sheeps is mysterious.
We can see that English plurals often become peculiar when there is a long vowel / diphthong before a final s: moose --> moose, mouse --> mice --> goose --> geese. House becomes houses, but the sound of the s becomes that of a z. Noose is one of the few compliant exceptions to this rule of oddity. We can theorise that moose not pluralising could also have something to do with it being a loanword from an exotic language, although Algonquian nouns apparently do, in general, have plural forms. On the other hand, mice and geese seem to reflect the pluralisation pattern of Old English: mus --> mys, gōs --> gēs.