The Collaborative International Dictionary of English v.0.48:

Only \On"ly\, a. [OE. only, anly, onlich, AS. [=a]nlic, i.e.,
   onelike. See One, and Like, a.]
   1. One alone; single; as, the only man present; his only
      occupation.
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   2. Alone in its class; by itself; not associated with others
      of the same class or kind; as, an only child.
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   3. Hence, (figuratively): Alone, by reason of superiority;
      preeminent; chief. "Motley's the only wear." --Shak.
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The Collaborative International Dictionary of English v.0.48:

Only \On"ly\, adv. [See Only, a.]
   1. In one manner or degree; for one purpose alone; simply;
      merely; barely.
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            And to be loved himself, needs only to be known.
      --Dryden.
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   2. So and no otherwise; no other than; exclusively; solely;
      wholly. "She being only wicked." --Beau. & Fl.
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            Every imagination . . . of his heart was only evil.
                                                  --Gen. vi. 5.
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   3. Singly; without more; as, only-begotten.
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   4. Above all others; particularly. [Obs.]
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            His most only elected mistress.       --Marston.
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The Collaborative International Dictionary of English v.0.48:

Only \On"ly\, conj.
   Save or except (that); -- an adversative used elliptically
   with or without that, and properly introducing a single fact
   or consideration.
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         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.
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WordNet (r) 3.0 (2006):

only
    adv 1: and nothing more; "I was merely asking"; "it is simply a
           matter of time"; "just a scratch"; "he was only a child";
           "hopes that last but a moment" [syn: merely, simply,
           just, only, but]
    2: without any others being included or involved; "was entirely
       to blame"; "a school devoted entirely to the needs of problem
       children"; "he works for Mr. Smith exclusively"; "did it
       solely for money"; "the burden of proof rests on the
       prosecution alone"; "a privilege granted only to him" [syn:
       entirely, exclusively, solely, alone, only]
    3: with nevertheless the final result; "He arrived only to find
       his wife dead"; "We won only to lose again in the next round"
    4: in the final outcome; "These news will only make you more
       upset"
    5: except that; "It was the same story; only this time she came
       out better"
    6: never except when; "call me only if your cold gets worse"
       [syn: only, only if, only when]
    7: as recently as; "I spoke to him only an hour ago"
    adj 1: being the only one; single and isolated from others; "the
           lone doctor in the entire county"; "a lonesome pine"; "an
           only child"; "the sole heir"; "the sole example"; "a
           solitary instance of cowardice"; "a solitary speck in the
           sky" [syn: lone(a), lonesome(a), only(a),
           sole(a), solitary(a)]
    2: exclusive of anyone or anything else; "she alone believed
       him"; "cannot live by bread alone"; "I'll have this car and
       this car only" [syn: alone(p), only]