tetrad

{{wiktionary|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 (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