ruby

Etymology 1

From Middle English ruby, rube, from Old French rubi, from Medieval Latin rubīnus.

noun

1. A clear, deep, red variety of corundum, valued as a precious stone.
   Although there are dozens of different types of gems, among the best known and most important are diamond, ruby and sapphire, emerald and other gem forms of the mineral beryl, chrysoberyl, tanzanite, tsavorite, topaz and jade. 2012-03, Lee A. Groat, “Gemstones”, in American Scientist, volume 100, number 2, archived from the original on 2012-06-14, page 128
2. (obsolete) A red spinel.
3. A deep red colour.
   ruby
4. (heraldry) The tincture red or gules.
   Elgin. Topaz a Saltier and Chief Ruby, on a Canton Pearl a Lyon Rampant Saphyr, which last is their paternal Coat; and the Field Topaz, and Saltier, and Chief Ruby, was the Arms of King Robert the Bruce, they altering the Field from Pearl (as he bore it) to Topaz. 1720, Francis Nichols, Rudiments of Honour, page 296
   The Field is Ruby, on a Bend Topaz, three Martlets Diamond. … Checkie Topaz and Saphire, a Fesse within a Bordure Ruby, by the Name of Clifford. 1726, John Guillim, The Banner Display'd; Or, an Abridgment of Guillim, page 504
   (1) Pearl, a Cross, Ruby, with the Effigies of our Saviour thereon, Topaz, born in Memory of one of the Family's fighting against the Turks. (2) Topaz, a Chief Indented, Saphire. (3) Ruby, three covered Cups, Topaz … 1754, John Lodge, The Peerage of Ireland; Or, a Genealogical History of the ..., page 71
5. (uncountable, printing, UK, dated) The size of type between pearl and nonpareil, standardized as 5½-point.
6. A ruby hummer, a South American hummingbird, Clytolaema rubricauda.
7. A red bird-of-paradise, Paradisaea rubra.

adj

1. Of a deep red colour.

verb

1. (transitive, poetic) To make red; to redden.

Etymology 2

From the British 5.5-point font Ruby, used for annotations in printed documents.

noun

1. A pronunciation guide written above or beside Chinese or Japanese characters.