copula

noun

1. A word, usually a verb, used to link the subject of a sentence with a predicate (usually a subject complement or an adverbial), that unites or associates the subject with the predicate.

   “I begin by arguing in section 2 that there are in fact at least two Celtic copulas, a grammatical copula that simply spells out tense and agreement, and a substantive copula formed on a lexically listed verbal stem.”

   “The theory of conjunctively tensed copulae will be developed and stated with more precision in the following section.”

   “This paper explores the position of the copula in the development of the verb system in second language acquisition of Italian.”

   “The present study focuses on the acquisition of a specific verbal element, namely the copula, in predicative constructions in a cross-linguistic perspective (English, German, Croatian).”

   “Lang Belta has no copula like English ‘is’.”

2. The bond or relationship by which two things are combined into a unity.

   “The fact that in milk the copula or bond is exceedingly slight is evident from the spontaneous resolution of milk when left in a vessel, its resolution, namely, into cream—a white substance of comparative consistency,—and a sourish fluid; also from its ready resolution when, merely by motion, it is turned into butter, or, by heat, into various kinds of curds.”

   “I quite correctly defined logical copulation by means [of] the copula of inclusion.”

3. A function that represents the association between two or more variables, independent of the individual marginal distributions of the variables.

   “In 2000, David X. Li, a banker with a doctorate in statistics who was then at RiskMetrics, part of J. P. Morgan Chase, began using mathematical functions called Gaussian copulas to estimate the likelihood of corporations’ dying in unison.”

   “There is little statistical theoretical theory for copulas. Sensitivity studies of estimation procedures and goodness-of-fit tests for copulas are unknown.”

   “Copulas provide an example of the haphazard evolution of quantitative finance. The key result is Sklar's theorem, which says that one can characterize any multivariate probability distribution by its copula (which specifies the correlation structure) and its marginal distributions (the conditional one dimensional distributions). Thus one can create multivariate distributions by mixing and matching copulas and marginal distributions.”

   “A recently developed flexible method is provided by hierarchical Archimedean copulae (HAC).”

4. A device that connects two or more keyboards of an organ.
5. The act of copulation; mating.