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. The term comes from the Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Eur ...

, 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) Meiosis () is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, the sperm or egg cells. It involves two rounds of division that ultimately result in four cells, each with only one copy ...

Tetrad (general relativity) In general relativity, a frame field (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 spaceti ...

, 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 independen ...

, an approach to general relativity * Tetrad (geometry puzzle), 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 an ...

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

, 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, or spelled nybble to match byte, is a unit of information that is an aggregation of four- bits; half of a byte/ octet. The unit is alternatively called nyble, nybl, half-byte or tetrade. In networking or telecommuni ...

, or tetrade, a 4-bit group * a

tuple In mathematics, a tuple is a finite sequence or ''ordered list'' of numbers or, more generally, mathematical objects, which are called the ''elements'' of the tuple. An -tuple is a tuple of elements, where is a non-negative integer. There is o ...

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