Proto-Indo-European root meaning "one, unique."

It forms all or part of: a (1) indefinite article; alone; an; Angus; anon; atone; any; eleven; inch (n.1) "linear measure, one-twelfth of a foot;" lone; lonely; non-; none; null; once; one; ounce (n.1) unit of weight; quincunx; triune; unanimous; unary; une; uni-; Uniate; unilateral; uncial; unicorn; union; unique; unison; unite; unity; universal; universe; university; zollverein.

It is the hypothetical source of/evidence for its existence is provided by: Greek oinos "ace (on dice);" Latin unus "one;" Old Persian aivam; Old Church Slavonic -inu, ino-; Lithuanian vienas; Old Irish oin; Breton un "one;" Old English an, German ein, Gothic ains "one."

"single as regards number, class, or kind," Middle English onli, from Old English ænlic, anlic "only, unique, solitary," literally "one-like," from an "one" (see one) + -lic "-like" (see -ly (1)). Similar formation in Old Frisian einlik, Dutch eenlijk, Old High German einlih, Danish einlig. It preserves the old pronunciation of one. Related: Onliness.

Its use as an adverb ("alone, no other or others than; in but one manner; for but one purpose") and conjunction ("but, except") developed in Middle English. Distinction of only and alone (now usually in reference to emotional states) is unusual; in many languages the same word serves for both. German also has a distinction in allein/einzig. Phrase only-begotten (mid-15c.) is biblical, translating Latin unigenitus, Greek monogenes; the Old English word was ancenned. Only child is attested by 1700.

1590s, "be in harmony, agree, be in accordance," from adverbial phrase atonen (c. 1300) "in accord," literally "at one," a contraction of at and one. It retains the older pronunciation of one.

The meaning "make up (for errors or deficiencies)" is from 1660s; that of "make reparations" is from 1680s.

Atone. To bring at one, to reconcile, and thence to suffer the pains of whatever sacrifice is necessary to bring about a reconciliation. [Hensleigh Wedgwood, "A Dictionary of English Etymology," 1859]

The phrase perhaps is modeled on Latin adunare "unite," from ad "to, at" (see ad-) + unum "one." Related: Atoned; atoning.

"unaccompanied, solitary; without companions," c. 1300, a contraction of all ane, from Old English all ana "unaccompanied, all by oneself," literally "wholly oneself," from all "all, wholly" (see all) + an "one" (see one). It preserves the old pronunciation of one.

Similar compounds are found in German (allein) and Dutch (alleen). The sense of "and nothing else" is from c. 1200, as in "Man does not live by bread alone" (Matthew iv.4, KJV; there Tyndale has "man shall not lyve by brede onlye"). Related: Aloneness. Adverbial alonely seems to have become obsolete 17c.

indefinite article before words beginning with vowels, 12c., from Old English an (with a long vowel) "one; lone," also used as a prefix meaning "single, lone" (as in anboren "only-begotten," anhorn "unicorn," anspræce "speaking as one"). See one for the divergence of that word from this. Also see a, of which this is the older, fuller form.

In other European languages, identity between the indefinite article and the word for "one" remains explicit (French un, German ein, etc.). Old English got by without indefinite articles: He was a good man in Old English was he wæs god man.

In texts of Shakespeare, etc., an as a word introducing a clause stating a condition or comparison conjunction is a reduced form of and in this now-archaic sense "if" (a usage first attested late 12c.), especially before it.

late Old English anon "straightway, forthwith," earlier on an, literally "into one," thus "continuously; straightway (in one course), at once;" see one. As a reply, "at once, coming!" By gradual misuse, "soon, in a little while" (1520s). An etymological one-word lesson in procrastination.

"any person or persons," 1844 as one word; since Old English as two words, from any + one. Old English also used ænigmon in this sense, Middle English eani mon, ani on; also compare anybody.

"1 more than ten; the number which is one more than ten; a symbol representing this number;" c. 1200, elleovene, from Old English enleofan, endleofan, literally "one left" (over ten), from Proto-Germanic *ainlif- (compare Old Saxon elleban, Old Frisian andlova, Dutch elf, Old High German einlif, German elf, Old Norse ellifu, Gothic ainlif), a compound of *ain "one" (see one) + from PIE root *leikw- "to leave."

FIREFLY: Give me a number from 1 to 10.

CHICOLINI: eleven!

FIREFLY: Right!

["Duck Soup"]

Viking survivors who escaped an Anglo-Saxon victory were daroþa laf "the leavings of spears," while hamora laf "the leavings of hammers" was an Old English kenning for "swords" (both from "The Battle of Brunanburh"). Twelve reflects the same formation. Outside Germanic the only instance of this formation is in Lithuanian, which uses -lika "left over" and continues the series to 19 (vienuo-lika "eleven," dvy-lika "twelve," try-lika "thirteen," keturio-lika "fourteen," etc.). Meaning "a team or side" in cricket or football is from 1743.

"every person, everybody," c. 1200, from every + one.

Middle English non, none, from Old English nan "not one, not any, no person; not the least part," from ne "not" (see no) + an "one" (see one). Cognate with Old Saxon, Middle Low German nen, Old Norse neinn, Middle Dutch, Dutch neen, Old High German, German nein "no," and analogous to Latin non- (see non-). It is thus the negative of one, an, and a (1).

As an adverb, "1650s, "by no means;" 1799 as "in no respect or degree, to no extent." As an adjective from late Old English; since c. 1600 reduced to no except in a few archaic phrases, especially before vowels, such as none other, none the worse.