Tetrad
# Tetrad

Tetrad ('group of 4') or tetrade may refer to:

* Tetrad (area), an area 2 km x 2 km square
* Tetrad (astronomy), four total lunar eclipses within two years
* Tetrad (chromosomal formation)
* Tetrad (general relativity), or frame field
   * Tetrad formalism, an approach to general relativity
* Tetrad (geometry puzzle), a set of four simply connected disjoint planar regions in the plane
* Tetrad (meiosis), the four cells produced by meiotic cell division
* Tetrad (music), a set of four notes
   * Tetrad (chord), a series of four notes
* Tetrad (symbol), or tetractys, a triangular figure of ten points arranged in four rows, and mystical symbol
* Medical tetrad, a group of four signs or symptoms which characterise a specific medical condition
* Nibble, or tetrade, a 4-bit group
* a tuple of length 4
* Tetrad Islands, in the Antarctic
