Webster's Revised Unabridged Dictionary · 1913

Only

Only , adjective

[Old English only, anly, onlich, Anglo-Saxon ānlic, that is, onelike. See One, and Like, a.]

1.
One alone; single; as, the only man present; his only occupation.
2.
Alone in its class; by itself; not associated with others of the same class or kind; as, an only child.
3.
Alone, by reason of superiority; preeminent; chief. [figuratively]
Motley's the only wear. — Shakespeare

Only , adverb

[See Only, a.]

1.
In one manner or degree; for one purpose alone; simply; merely; barely.
And to be loved himself, needs only to be known.
2.
So and no otherwise; no other than; exclusively; solely; wholly.
She being only wicked. — Beau. & Fl
Every imagination... of his heart was only evil. — Gen. vi. 5
3.
Singly; without more; as, only-begotten.
4.
Above all others; particularly. [Obsolete]
His most only elected mistress. — Marston

Only , conjunction

Save or except (that); -- an adversative used elliptically with or without that, and properly introducing a single fact or consideration.
He might have seemed some secretary or clerk... only that his low, flat, unadorned cap... indicated that he belonged to the city. — Sir W. Scott