What is "triquetrum"

Triquetrum \Tri*que"trum\, n.; pl. Triquetra. [NL.] (Anat.) One of the bones of the carpus; the cuneiform. See Cuneiform (b) .

n. 1 (context anatomy English) The triquetral bone 2 An astronomical instrument.

The triquetrum (derived from the Latin tri- ["three"] and quetrum ["cornered"]) was the medieval name for an ancient astronomical instrument first described by Ptolemy (c. 90–c. 168) in the Almagest (V. 12). Also known as Parallactic Rulers, it was used for determining altitudes of heavenly bodies. Ptolemy calls it a "parallactic instrument" and seems to have used it to determine the zenith distance and parallax of the Moon.

Triquetrum may refer to:

• triquetrum (astronomy), an ancient astronomical instrument
• The triquetral bone in the human wrist

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