1.  only(s = adj.all) lone, lonesome, sole, solitary - 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"

2.  only(s = adj.all) alone - exclusive of anyone or anything else; "she alone believed him"; "cannot live by bread alone"; "I'll have this car and this car only"

1.  only(r = adv.all) but, just, merely, simply - 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"

2.  only(r = adv.all) alone, entirely, exclusively, solely - 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"

3.  only(r = adv.all) Array - with nevertheless the final result; "He arrived only to find his wife dead"; "We won only to lose again in the next round"

4.  only(r = adv.all) Array - in the final outcome; "These news will only make you more upset"

5.  only(r = adv.all) Array - except that; "It was the same story; only this time she came out better"

6.  only(r = adv.all) only if, only when - never except when; "call me only if your cold gets worse"

7.  only(r = adv.all) Array - as recently as; "I spoke to him only an hour ago"

1.  One alone; single; as, the only man present; his only occupation. [1913 Webster]

2.  Alone in its class; by itself; not associated with others of the same class or kind; as, an only child. [1913 Webster]

3.  Alone, by reason of superiority; preëminent; chief. Shak. [1913 Webster]

1.  In one manner or degree; for one purpose alone; simply; merely; barely. [1913 Webster]
"And to be loved himself, needs only to be known." Dryden. [1913 Webster]

2.  So and no otherwise; no other than; exclusively; solely; wholly. Beau. & Fl. [1913 Webster]
"Every imagination . . . of his heart was only evil." [1913 Webster]

3.  Singly; without more; as, only-begotten. [1913 Webster]

4.  Above all others; particularly. [1913 Webster]
"His most only elected mistress." [1913 Webster]

   Save or except (that); -- an adversative used elliptically with or without that, and properly introducing a single fact or consideration. [1913 Webster]
"He might have seemed some secretary or clerk . . . only that his low, flat, unadorned cap . . . indicated that he belonged to the city." [1913 Webster]

only, adv., adj., & conj.
--adv.
1 solely, merely, exclusively; and no one or nothing more besides (I only want to sit down; will only make matters worse; needed six only; is only a child).
2 no longer ago than (saw them only yesterday).
3 not until (arrives only on Tuesday).
4 with no better result than (hurried home only to find her gone).

Idiom:
only-begotten literary begotten as the only child. only too extremely (is only too willing).

Usage:
In informal English only is usually placed between the subject and verb regardless of what it refers to (e.g. I only want to talk to you); in more formal English it is often placed more exactly, esp. to avoid ambiguity (e.g. I want to talk only to you). In speech, intonation usually serves to clarify the sense.
--attrib.adj.
1 existing alone of its or their kind (their only son).
2 best or alone worth knowing (the only place to eat).
--conj. colloq.
1 except that; but for the fact that (I would go, only I feel ill).
2 but then (as an extra consideration) (he always makes promises, only he never keeps them).

Etymology:
OE anlic, {aelig}nlic, ME onliche (as ONE, -LY(2))

N  imperfection, imperfectness, deficiency, inadequacy, peccancy, immaturity, fault, defect, weak point, screw loose, flaw, gap, twist, taint, attainder, bar sinister, hole in one's coat, blemish, weakness, half blood, shortcoming, drawback, seamy side, mediocrity, no great shakes, no great catch, not much to boast of, one-horse shay, imperfect, not perfect, deficient, defective, faulty, unsound, tainted, out of order, out of tune, cracked, leaky, sprung, warped, lame, injured, peccant, frail, inadequate, crude, incomplete, found wanting, below par, short-handed, below its full strength, under its full strength, below its full complement, indifferent, middling, ordinary, mediocre, average, so-so, coucicouci, milk and water, tolerable, fair, passable, pretty well, pretty good, rather good, moderately good, good, good enough, well enough, adequate, decent, not bad, not amiss, inobjectionable, unobjectionable, admissible, bearable, only better than nothing, secondary, inferior, second-rate, second-best, one-horse, almost, to a limited extent, rather, pretty, moderately, passing, only, considering, all things considered, enough, surgit amari aliquid.

N  smallness, littleness, tenuity, paucity, fewness, meanness, insignificance (unimportance), mediocrity, moderation, small quantity, modicum, trace, hint, minimum, vanishing point, material point, atom, particle, molecule, corpuscle, point, speck, dot, mote, jot, iota, ace, minutiae, details, look, thought, idea, soupcon, dab, dight, whit, tittle, shade, shadow, spark, scintilla, gleam, touch, cast, grain, scruple, granule, globule, minim, sup, sip, sop, spice, drop, droplet, sprinkling, dash, morceau, screed, smack, tinge, tincture, inch, patch, scantling, tatter, cantlet, flitter, gobbet, mite, bit, morsel, crumb, seed, fritter, shive, snip, snippet, snick, snack, snatch, slip, scrag, chip, chipping, shiver, sliver, driblet, clipping, paring, shaving, hair, nutshell, thimbleful, spoonful, handful, capful, mouthful, fragment, fraction, drop in the ocean, animalcule, trifle, mere nothing, next to nothing, hardly anything, just enough to swear by, the shadow of a shade, finiteness, finite quantity, small, little, diminutive, minute, fine, inconsiderable, paltry, faint, slender, light, slight, scanty, scant, limited, meager, sparing, few, low, so-so, middling, tolerable, no great shakes, below par, under par, below the mark, at a low ebb, halfway, moderate, modest, tender, subtle, inappreciable, evanescent, infinitesimal, homeopathic, very small, atomic, corpuscular, microscopic, molecular, subatomic, mere, simple, sheer, stark, bare, near run, dull, petty, shallow, stolid, ungifted, unintelligent, to a small extent, on a small scale, a little bit, a wee bit, slightly, imperceptibly, miserably, wretchedly, insufficiently, imperfectly, faintly, passably, pretty well, well enough, partially, in part, in a certain degree, to a certain degree, to a certain extent, comparatively, some, rather in some degree, in some measure, something, somewhat, simply, only, purely, merely, at least, at the least, at most, at the most, ever so little, as little as may be, tant soit peu, in ever so small a degree, thus far, pro tanto, within bounds, in a manner, after a fashion, so to speak, almost, nearly, well-nigh, short of, not quite, all but, near upon, close upon, peu s'en faut, near the mark, within an ace of, within an inch of, on the brink of, scarcely, hardly, barely, only just, no more than, about, thereabouts, somewhere about, nearly, say, be the same, be little more or less, no ways, no way, no wise, not at all, not in the least, not a bit, not a bit of it, not a whit, not a jot, not a shadow, in no wise, in no respect, by no means, by no manner of means, on no account, at no hand, dare pondus idonea fumo, magno conatu magnas nugas, small sands the mountain, moments make the year.

N  simpleness, purity, homogeneity, elimination, sifting, purification, simple, uniform, of a piece, homogeneous, single, pure, sheer, neat, unmixed, unmingled, unblended, uncombined, uncompounded, elementary, undecomposed, unadulterated, unsophisticated, unalloyed, untinged, unfortified, pur et simple, incomplex, free from, exempt from, exclusive, simple, only.

N  unity, oneness, individuality, solitude, isolation, unification, one, unit, ace, individual, none else, no other, one, sole, single, solitary, unitary, individual, apart, alone, kithless, unaccompanied, unattended, solus, single-handed, singular, odd, unique, unrepeated, azygous, first and last, isolated, insular, monospermous, unific, uniflorous, unifoliate, unigenital, uniliteral, unijocular, unimodal, unimodular, lone, lonely, lonesome, desolate, dreary, insecable, inseverable, indiscerptible, compact, indivisible, atomic, irresolvable, singly, alone, by itself, per se, only, apart, in the singular number, in the abstract, one by one, one at a time, simply, one and a half, sesqui-, natura il fece, e poi roppe la stampa, du fort au faible, two souls with but a single thought, two hearts that beat as one.

in name only, not only, one and only, only if, only too, only when, standing room only