third person singular present indicative suffix of verbs, it represents Old English -es, -as, which began to replace -eð in Northumbrian 10c., and gradually spread south until by Shakespeare's time it had emerged from colloquialism and -eth began to be limited to more dignified speeches.
suffix forming almost all Modern English plural forms of nouns, gradually extended in Middle English as -es from Old English -as, the nominative plural and accusative plural ending of certain "strong" masculine nouns (such as dæg "day," nominative/accusative plural dagas "days"). The commonest Germanic declension, traceable back to the original PIE inflection system, it is also the source of the Dutch -s plurals and (by rhotacism) Scandinavian -r plurals (such as Swedish dagar).
Much more uniform today than originally; Old English also had a numerous category of "weak" nouns that formed their plurals in -an, and other strong nouns that formed plurals with -u. Quirk and Wrenn, in their Old English grammar, estimate that 45 percent of the nouns a student will encounter will be masculine, nearly four-fifths of them with genitive singular -es and nominative/accusative plural in -as. Less than half, but still the largest chunk.
The triumphs of -'s possessives and -s plurals represent common patterns in language: using only a handful of suffixes to do many jobs (such as -ing), and the most common variant squeezing out the competition. To further muddy the waters, it's been extended in slang since 1936 to singulars (such as ducks, sweets, babes) as an affectionate or diminutive suffix.
Old English single-syllable collectives (sheep, folk) as well as weights, measures, and units of time did not use -s. The use of it in these cases began in Middle English, but the older custom is preserved in many traditional dialects (ten pound of butter; more than seven year ago; etc.).
before vowels sarc-, word-forming element in science meaning "flesh, fleshy, of the flesh;" from Latinized form of Greek sark-, combining form of sarx "flesh," traditionally derived from a PIE root *twerk-, *tuerk- "to cut" (source also of Avestan thwares "to cut"), but Beekes is dubious.
element used in forming dinosaur names, from Latinized form of Greek sauros "lizard," a word of unknown origin; possibly related to saulos "twisting, wavering."
word-forming element meaning "division; split, cleavage," from Latinized form of Greek skhizo-, combining form ("irregular," says OED) of skhizein "to split, cleave, part, separate" (from PIE root *skei- "to cut, split").
before vowels scler-, word-forming element meaning "hard," from Latinized form of Greek sklēros "hard, harsh," which is related to skellein "to dry up, parch" (from PIE *skle-ro-, from root *skele- "to parch, wither").
word-forming element indicating "an instrument for seeing," from Late Latin -scopium, from Greek -skopion, from skopein "to look at, examine" (from PIE root *spek- "to observe").
word-forming element meaning "viewing, examining, observing," from Modern Latin -scopium, from Greek -skopion, from skopein "to look at, examine" (from PIE root *spek- "to observe").
word-forming element meaning "quality, condition; act, power, skill; office, position; relation between," Middle English -schipe, from Old English -sciepe, Anglian -scip "state, condition of being," from Proto-Germanic *-skepi- (cognates: Old Norse -skapr, Danish -skab, Old Frisian -skip, Dutch -schap, German -schaft), from *skap- "to create, ordain, appoint," from PIE root *(s)kep-, forming words meaning "to cut, scrape, hack" (see shape (v.)). It often forms abstracts to go with corresponding concretes (friend/friendship, etc.).
