Forming adverbs, was originally -es, identical with the suffix of the genitive singular of many neuter and masculine nouns and adjectives. Several of the adverbs in -es that existed in Old English are genitives either of nouns (neuter or masculine) as dæges by day, nédes needs adv., þances voluntarily, or of neuter adjectives, as sóðes truly; on the analogy of these, -es was added, with adverb-forming function, to feminine nouns, as in nihtes by night, endebyrdes in order. Old English had also adverbs compounded of tó preposition and a genitive governed by it, as tó-gegnes (see to-gains prep.), tó-middes (see tomids adv. and prep.); side by side with these there existed parallel and synonymous adverbs like on-gegn again adv., prep., and conj., on-middan amid prep. and adv., in which the dative or accusative was governed by a preposition. Hence there arose in early Middle English mixed forms such as aȝeines, amiddes; and the frequent coexistence of the two forms of the same adverb, one with and the other without s, led to the addition of s to many adverbs as a sign of their function. In some instances the extended form prevailed, as in eftsoons; in others it survived only in dialects, as in oftens, gaylies (Scottish). See also the articles -ling suffix², -lings suffix, -ward suffix, -wards suffix, -way comb. form, -ways comb. form. In once, twice, thrice, hence, since, etc., the suffix is written differently. In against prep., conj., adv., and n., alongst prep. and adv., amongst prep., amidst adv., prep., and n., and the dialectal onst (see once adv., conj., adj., and n.), the original -es, -s has become -st.

A shortened form of the hypocoristic diminutive suffix -sy suffix¹, added to the same classes of words, as Babs, Toots; ducks (see duck n.¹ 3c), moms.