as

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun An ancient Roman coin of copper or copper alloy.
• noun An ancient Roman unit of weight equal to about one troy pound.

from The Century Dictionary.

• noun In Latin, an integer; a whole or single thing; especially, a unit divided into twelve parts. Thus, the jugerum was called an as.
• noun As a unit of weight, 12 ounces (Latin unciœ, twelfths); the libra or pound, equal to 325.8 grams, or 5,023 grains.
• noun A copper coin, the unit of the early monetary system of Rome.
• noun . Obsolete form of ace. Chaucer.
• noun An old Swedish and Dutch unit of weight, equal to 4.8042 centigrams, or about three quarters of a troy grain. See asducat and ass.
• noun Chemical symbol of arsenic.
• An obsolete and dialectal or colloquial form of has: in colloquial speech often further reduced to 's: as, who's been here?
• noun An assimilated form of ad- before s, as in assimilate, assert, assume, etc.
• noun An erroneously restored form of a-, originally Latin ab-, in assoil, assoilzie, from the Latin absolvere, absolve.
• noun A variant of es-, Latin ex-, in assart, assay, astonish, obsolete ascape, aschew, assaumple, etc.; now represented also, or only, by es-, as in escape, eschew, or s-, as in scape, sample. See es.
• noun In Norse myth., one of the gods, the inhabitants of Asgard. See Asgard.
• The antecedent in the correlation as … so, or as … as: In that degree; to that extent; so far.
• The relative clause is often omitted, especially in colloquial speech, being inferred from the antecedent: as, this will do as well (sc. as that); I would as lief walk (sc. as ride).
• The consequent in the correlations as … as, so … as, such … as, same … as, etc., expressing quantity, degree, proportion, manner, etc.
• The antecedent as is often, and so is usually, omitted: as, black as jet; cold as ice; do as you like.
• In parenthetical clauses involving a concession, the relative as (the antecedent being omitted) may be equivalent to though: as, late as it was, we set forth on our journey.
• In parenthetical clauses involving a contrast or negation as to fact with the principal clause, as approaches an adversative sense, being nearly equivalent to but.
• In subordinate clauses involving a supposition, as is conditional, being equivalent to as if, as though, which are the ordinary forms. This use is now rare or only poetical except in the independent phrase as it were. (See phrases below.)
• The clause introduced by as may be reduced by ellipsis of its verb and other elements to one or two important words, leaving as as a quasi-connective: Between an adverb or adverbial phrase in the principal clause and an adverb or adverbial phrase constituting the subordinate clause.
• Between the principal verb or its subject and the subordinate subject or object, which becomes equivalent to a predicate appositive or factitive object after the principal verb, as meaning ‘after the manner of,’ ‘the same as,’ ‘like,’ ‘in the character or capacity of,’ etc.: as, the audience rose as one man; all these things were as nothing to him; he has been nominated as a candidate. Hence in constructions where the appositive clause depends directly upon the noun: as, his career as a soldier was brilliant; his reputation as a scholar stands high: and so in naming phases of a general subject: as, Washington as a general; man as a thinker. The construction as a quasi-predicate appositive or factitive object after a principal verb is usual after verbs of seeming or regarding.
• The subordinate clause introduced by as is often not dependent grammatically upon the principal verb, but serves to restrict or determine the scope of the statement as a whole. Such clauses are parenthetical, and usually elliptical, some of them, as as usual and as a rule, having almost the idiomatical unity of an adverbial phrase.
• In certain emphatic formulas, as (‘even as’) introduces a solemn attestation (‘as truly or surely as’) or adjuration (‘in a manner befitting the fact that’), approaching a causal sense, ‘since, because.’ (See 2, below.)
• Of reason: Since; because; inasmuch as.
• Of time: When; while; during the time that.
• Of purpose or result: The consequent in the correlations so … as, such … as: To such a degree that; in such a manner that: followed by an infinitive or, formerly, by a finite verb (but in the latter construction that has taken the place of as).
• Of mere continuation, introducing a clause in explanation or amplification of a word or statement in the principal clause, especially in giving examples: For example; for instance; to wit; thus.
• In dependent clauses: That.
• After comparatives: Than.
• Before certain adverbs and adverbial phrases, including prepositional phrases: Even; just: restricting the application to a particular point: as, as now, as then, as yet, as here, as there, etc.
• Before prepositional phrases as becomes attached in thought to the preposition, making practically a new prepositional unit. See as anent, as concerning, as for, etc., below.
• That; who; which: after such or same, and introducing an attributive clause: as, he did not look for such a result as that; he traveled the same route as I did.

from the GNU version of the Collaborative International Dictionary of English.

• noun A Roman weight, answering to the libra or pound, equal to nearly eleven ounces Troy weight. It was divided into twelve ounces.
• noun A Roman copper coin, originally of a pound weight (12 oz.); but reduced, after the first Punic war, to two ounces; in the second Punic war, to one ounce; and afterwards to half an ounce.
• noun (Chem.) the chemical symbol for arsenic.
• adverb Denoting equality or likeness in kind, degree, or manner; like; similar to; in the same manner with or in which; in accordance with; in proportion to; to the extent or degree in which or to which; equally; no less than
• adverb In the idea, character, or condition of, -- limiting the view to certain attributes or relations
• adverb While; during or at the same time that; when.
• adverb Because; since; it being the case that.
• adverb Expressing concession. (Often approaching though in meaning).
• adverb obsolete That, introducing or expressing a result or consequence, after the correlatives so and such.
• adverb [Obs.] so that.
• adverb Obs. or Poetic As if; as though.
• adverb For instance; by way of example; thus; -- used to introduce illustrative phrases, sentences, or citations.
• adverb Obs. & R. Than.
• adverb obsolete Expressing a wish.
• adverb See So . . as, under So.
• adverb to the extent or degree.
• adverb [Obs.] as far as.