alone (adj., adv.)

"unaccompanied, solitary; without companions, solitary," c. 1300 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). Sense of "and nothing else" ("Man shall not live on bread alone") is from c. 1200. Related: Aloneness. Adverbial alonely seems to be obsolete since 17c.

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Definitions of alone
alone (adj.)
exclusive of anyone or anything else;
cannot live by bread alone
she alone believed him
Synonyms: only
alone (adj.)
isolated from others;
I want to be alone
could be alone in a crowded room
was alone with her thoughts
alone (adj.)
lacking companions or companionship;
she is alone much of the time
he was alone when we met him
Synonyms: lone / lonely / solitary
alone (adj.)
radically distinctive and without equal;
he is alone in the field of microbiology
this theory is altogether alone in its penetration of the problem
Synonyms: unique / unequaled / unequalled / unparalleled
alone (adv.)
without any others being included or involved;
the burden of proof rests on the prosecution alone
Synonyms: entirely / exclusively / solely / only
alone (adv.)
without anybody else or anything else;
the pillar stood alone, supporting nothing
the child stayed home alone
Synonyms: solo / unaccompanied