- A precious stone consisting of corundum with trace chromium impurity atoms, which give it its transparent red appearance. Used, for instance, in precision instruments such as lasers.
- noun an old printing size, similar to five point
Origin & History of “ruby”
Ruby goes back ultimately to Latin ruber ‘red’, a descendant of the same Indo-European base as produced English red. From it was derived the medieval Latin adjective rubīnus, which was used in the term lapis rubīnus ‘red stone’. In due course rubīnus itself came to be employed as a noun in this sense, and it passed into English via Old French rubi. other English words from the same source include rubella (19th c.), rubicund (16th c.), rubidium (19th c.), and rubric (14th c.) (headings in ancient and medieval manuscripts were often written in red ink).