The Collaborative International Dictionary of English v.0.48:

Derivation \Der`i*va"tion\, n. [L. derivatio: cf. F.
   d['e]rivation. See Derive.]
   1. A leading or drawing off of water from a stream or source.
      [Obs.] --T. Burnet.
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   2. The act of receiving anything from a source; the act of
      procuring an effect from a cause, means, or condition, as
      profits from capital, conclusions or opinions from
      evidence.
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            As touching traditional communication, . . . I do
            not doubt but many of those truths have had the help
            of that derivation.                   --Sir M. Hale.
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   3. The act of tracing origin or descent, as in grammar or
      genealogy; as, the derivation of a word from an Aryan
      root.
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   4. The state or method of being derived; the relation of
      origin when established or asserted.
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   5. That from which a thing is derived.
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   6. That which is derived; a derivative; a deduction.
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            From the Euphrates into an artificial derivation of
            that river.                           --Gibbon.
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   7. (Math.) The operation of deducing one function from
      another according to some fixed law, called the law of
      derivation, as the operation of differentiation or of
      integration.
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   8. (Med.) A drawing of humors or fluids from one part of the
      body to another, to relieve or lessen a morbid process.
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   9. The formation of a word from its more original or radical
      elements; also, a statement of the origin and history of a
      word.
      [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

derivation
    n 1: the source or origin from which something derives (i.e.
         comes or issues); "he prefers shoes of Italian derivation";
         "music of Turkish derivation"
    2: (historical linguistics) an explanation of the historical
       origins of a word or phrase [syn: deriving, derivation,
       etymologizing]
    3: a line of reasoning that shows how a conclusion follows
       logically from accepted propositions
    4: (descriptive linguistics) the process whereby new words are
       formed from existing words or bases by affixation; "`singer'
       from `sing' or `undo' from `do' are examples of derivations"
    5: inherited properties shared with others of your bloodline
       [syn: ancestry, lineage, derivation, filiation]
    6: drawing of fluid or inflammation away from a diseased part of
       the body
    7: drawing off water from its main channel as for irrigation
    8: the act of deriving something or obtaining something from a
       source or origin

Moby Thesaurus II by Grady Ward, 1.0:

188 Moby Thesaurus words for "derivation":
   IC analysis, acceptance, accidence, acquisition, admission,
   admittance, adoption, affiliation, affix, affixation, allomorph,
   ancestry, apparentation, appropriation, assumption, beginning,
   birth, blood, bloodline, borrowed plumes, bound morpheme,
   bowwow theory, branch, breed, by-product, cognate, commencement,
   common ancestry, comparative linguistics, conception, conclusion,
   conjugation, consanguinity, consequence, consequent, copying,
   corollary, cutting, declension, deduction, derivative, deriving,
   descent, descriptive linguistics, development, dialectology,
   difference of form, dingdong theory, direct line, distaff side,
   distillate, doublet, effect, enclitic, eponym, eponymy, etymology,
   etymon, event, eventuality, eventuation, extraction, family,
   female line, filiation, folk etymology, formative, foundation,
   fountain, free form, fruit, genealogy, genesis, getting,
   glossematics, glossology, glottochronology, glottology, grammar,
   graphemics, grass roots, harvest, head, historical linguistics,
   house, illation, imitation, immediate constituent analysis,
   inception, induction, inference, infix, infixation, inflection,
   infringement, issue, language study, legacy, lexicology,
   lexicostatistics, line, line of descent, lineage,
   linguistic geography, linguistic science, linguistics,
   logical outcome, male line, mathematical linguistics, mocking,
   morph, morpheme, morphemic analysis, morphemics, morphology,
   morphophonemics, offshoot, offspring, origin, original,
   origination, outcome, outgrowth, paleography, paradigm, pasticcio,
   pastiche, philology, phonetics, phonology, phylum, pirating,
   plagiarism, plagiary, precipitate, prefix, prefixation, primitive,
   proclitic, product, provenance, provenience, psycholinguistics,
   race, radical, radix, receipt, receival, receiving, reception,
   result, resultant, rise, root, seed, semantic history, semantics,
   sept, sequel, sequela, sequence, sequent, side, simulation,
   sociolinguistics, source, spear side, spindle side, stem, stirps,
   stock, strain, structuralism, succession, suffix, suffixation,
   sword side, syntactics, taking, taproot, theme,
   transformational linguistics, upshot, well, wellspring, whence,
   word history, word-formation