comma

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. Grammar A punctuation mark ( , ) used to indicate a separation of ideas or of elements within the structure of a sentence.
2. n. A pause or separation; a caesura.
3. n. Any of several butterflies of the genus Polygonia, having wings with brownish coloring and irregularly notched edges.

Century Dictionary and Cyclopedia

1. n. In ancient Grammar and rhetoric, a group of a few words only; a phrase or short clause, forming part of a colon or longer clause.
2. n. In ancient prosody: A fragment or smaller section of a colon; a group of a few words or feet not constituting a complete metrical series.
3. n. The part of a dactylic hexameter ending with, or that beginning with, the cesura; also, the cesura itself.
4. n. A clause.
5. n. In rhetoric, a slight pause between two phrases, clauses, or words.
6. n. In musical acoustics: The interval between the octave of a given tone and the tone produced by taking six successive whole steps from the given tone, represented by the ratios , or 531441:524288. Also called the Pythagorean comma, or comma maxima.
7. n. The interval between the larger and the smaller whole steps, represented by the ratio , or 81:80. Also called the Didymic or syntonic comma.
8. n. In punctuation, a point (,) used to indicate the smallest interruptions in continuity of thought or grammatical construction, the marking of which contributes to clearness.
9. n. A spot or mark shaped like such a comma.
10. n. In entomology: A butterfly, Grapta comma-album: so named from a comma-shaped white mark on the under side of the wings.
11. n. [capitalized] [NL.] A genus of lepidopterous insects.

Wiktionary

1. n. Punctuation mark (,) (usually indicating a pause between parts of a sentence or between elements in a list).
2. n. by extension A diacritical mark used below certain letters in Romanian.
3. n. A European and North American butterfly, Polygonia c-album, of the family Nymphalidae.
4. n. music a small or very small interval between two enharmonic notes tuned in different ways.

GNU Webster's 1913

1. n. A character or point [,] marking the smallest divisions of a sentence, written or printed.
2. n. (Mus.) A small interval (the difference between a major and minor half step), seldom used except by tuners.

WordNet 3.0

1. n. a punctuation mark (,) used to indicate the separation of elements within the grammatical structure of a sentence
2. n. anglewing butterfly with a comma-shaped mark on the underside of each hind wing