The Collaborative International Dictionary of English v.0.48:

Commentary \Com"men*ta*ry\, n.; pl. Commentaries. [L.
   commentarius, commentarium, note book, commentary: cf. F.
   commentaire. See Comment, v. i.]
   1. A series of comments or annotations; esp., a book of
      explanations or expositions on the whole or a part of the
      Scriptures or of some other work.
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            This letter . . . was published by him with a severe
            commentary.                           --Hallam.
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   2. A brief account of transactions or events written hastily,
      as if for a memorandum; -- usually in the plural; as,
      Caesar's Commentaries on the Gallic War.
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