triple
tuple of arity 3
signature
number of positive, negative and zero eigenvalues of a metric tensor
Eisenstein triple
set of integers, the lengths of the sides of a triangle with a 60° angle
trigraph
group of three characters used to represent a single sound or a combination of sounds that does not correspond to the written letters combined
amicable triple
integer triplet like 103340640,123228768,124015008
rigged Hilbert space
Hilbert space equipped with a dense subspace that carries (in addition to the subspace topology) a finer topology such that the inclusion map is continuous
monad
monoid in an endofunctor category
Pythagorean triple
three positive integers, the squares of two of which sum to the square of the third