commentary

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

• noun Explanation or interpretation in the form of a series of comments or observations.
• noun An ongoing series of spoken remarks, especially during a television or radio broadcast of an event.
• noun An apt explanation or illustration.
• noun An expository treatise or series of annotations; an exegesis.
• noun A narrative of historical events of which one has personal experience.

from The Century Dictionary.

• noun A series or collection of comments or annotations; especially, an explanation or elucidation of difficult and obscure passages in a book or other writing, and consideration of questions suggested by them, arranged in the same order as in the text or writing examined; an explanatory essay or treatise: as, a commentary on the Bible. A textual commentary explains the author's meaning, sentence by sentence.
• noun Anything that serves to explain or illustrate; an exemplification.
• noun A historical narrative; an explanatory record of particular transactions: as, the Commentaries of Cæsar.
• noun Synonyms See remark, n.
• To write notes or comments.
• To comment upon.

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

• noun 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.
• noun A brief account of transactions or events written hastily, as if for a memorandum; -- usually in the plural.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A series of comments or annotations; especially, a book of explanations or expositions on the whole or a part of some other work.
• noun 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.
• noun An oral description of an event, especially broadcast by television or radio, as it occurs.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a written explanation or criticism or illustration that is added to a book or other textual material