Definition of trinomial in English:

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Pronunciation: /trʌɪˈnəʊmɪəl/


1(Of an algebraic expression) consisting of three terms.
Example sentences
  • In 1881 Gyula Farkas published a paper on Farkas Bolyai's iterative solution to the trinomial equation, making a careful study of the convergence of the algorithm.
  • There are many other forgeries in the paper to do with primes, Catalan numbers, binomial and trinomial numbers, mixing some genuine examples with the forgeries.
  • We use the likelihood ratio test on the trinomial probability of the number of nucleotide substitutions over codon positions under the two models and under observed sequence evolution.
2 Biology (Of a taxonomic name) consisting of three terms where the first is the name of the genus, the second that of the species, and the third that of the subspecies or variety.
Example sentences
  • A more recent estimate puts the total number of species at 436 ‘species’ (352 Demospongiae, 49 Calcarea, 35 Hexactinellida) if trinomial taxa, subspecies and varieties are included (R. W. M. van Soest, unpublished data).
  • The species were initially described as races by Forsman, but were elevated to species level by Bocquet, who considered them as members of the superspecies J. marina and gave them trinomial names.
  • The trinomial naming system has been abandoned in favor of the usual binomial naming convention.


1An algebraic expression of three terms.
Example sentences
  • In general, you will be trying to factor quadratic trinomials that look like a * y ^ 2 + b * y + c where a, b, and c are expressions not involving y…
  • Al-Khwarizmi's concept of algebra can now be grasped with greater precision: it concerns the theory of linear and quadratic equations with a single unknown, and the elementary arithmetic of relative binomials and trinomials.…
  • A trinomial is the sum of three monomials.
2 Biology A trinomial taxonomic name.
Example sentences
  • Geographical variation in morphology has been documented in N. mediocris for many years via the recognition of trinomials (subspecies: N. m. mediocris, usambarica, fuelleborni, and bensoni.)
  • Chronomorphs are recognized by a trinomial preceded by a ‘slash’ mark, such as in Ondatra zibethicus Imeadensis.
  • Many invalid trinomials will persist until someone takes the time to quantify them and reassess their validity.


Late 17th century: from tri- 'three', on the pattern of binomial.

For editors and proofreaders

Line breaks: tri|nomial

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