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

Tetrad (area) A tetrad is an area 2 km x 2 km square. The term refers to any of the 25 such squares which make up a standard hectad A hectad is an area 10 km x 10 km square. The term has a particular use in connection with the British Ordnan ...

, an area 2 km x 2 km square *

Tetrad (astronomy) In astronomy, a tetrad is a set of four total lunar eclipses within two consecutive years.Tetrad (chromosomal formation) 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 ** Tetra ...

Tetrad (general relativity) A frame field in general relativity (also called a tetrad or vierbein) is a set of four pointwise-orthonormal vector fields, one timelike and three spacelike, defined on a Lorentzian manifold that is physically interpreted as a model of spacetime ...

, or frame field **

Tetrad formalism The tetrad formalism is an approach to general relativity that generalizes the choice of basis for the tangent bundle from a coordinate basis to the less restrictive choice of a local basis, i.e. a locally defined set of four linearly independe ...

, an approach to general relativity *

Tetrad (geometry puzzle) In geometry, a tetrad is a set of four simply connected disjoint planar regions in the plane, each pair sharing a finite portion of common boundary. It was named by Michael R. W. Buckley in 1975 in the Journal of Recreational Mathematics. A furt ...

, a set of four simply connected disjoint planar regions in the plane *

Tetrad (meiosis) The tetrad is the four spores produced after meiosis of a yeast or other Ascomycota, ''Chlamydomonas'' or other alga, or a plant. After parent haploids mate, they produce diploids. Under appropriate environmental conditions, diploids sporulate and ...

, the four cells produced by meiotic cell division *

Tetrad (music) A tetrad is a set of four notes in music theory. When these four notes form a tertian chord they are more specifically called a ''seventh chord'', after the diatonic interval from the root of the chord to its fourth note (in root position close ...

, a set of four notes **

Tetrad (chord) In music theory, a tetrachord ( el, τετράχορδoν; lat, tetrachordum) is a series of four notes separated by three intervals. In traditional music theory, a tetrachord always spanned the interval of a perfect fourth, a 4:3 frequency propo ...

, a series of four notes *

Tetrad (symbol) The tetractys ( el, τετρακτύς), or tetrad, or the tetractys of the decad is a triangular number, triangular figure consisting of ten points arranged in four rows: one, two, three, and four points in each row, which is the geometrical repr ...

, 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 In computing, a nibble (occasionally nybble, nyble, or nybl to match the spelling of byte) is a four-bit aggregation, or half an octet. It is also known as half-byte or tetrade. In a networking or telecommunication context, the nibble is oft ...

, or tetrade, a 4-bit group * a

tuple In mathematics, a tuple is a finite ordered list (sequence) of elements. An -tuple is a sequence (or ordered list) of elements, where is a non-negative integer. There is only one 0-tuple, referred to as ''the empty tuple''. An -tuple is defi ...

of length 4 *

Tetrad Islands Tetrad Islands is a group of small islands lying southeast of Borge Point at Mikkelsen Harbor on Trinity Island in the Palmer Archipelago. They were shown on a 1952 Argentine government chart. The name given by the United Kingdom Antarctic Place ...

, in the Antarctic

See also