From Wiktionary, the free dictionary

From Middle English triangulare, trianguler, triangulere, from Old French triangulaire, triangulier and Latin triangulāris. By surface analysis, tri- +‎ -angular.

• (UK) IPA^(key): /tɹaɪˈæŋ.ɡjə.lə/, /tɹaɪˈæŋ.ɡjʊ.lə/
• (US) IPA^(key): /tɹaɪˈæŋ.ɡjə.lɚ/, /tɹaɪˈaɪŋ.ɡjʊ.lɚ/

triangular (comparative more triangular, superlative most triangular)

1. Shaped like a triangle.

   • 1963, Margery Allingham, “Foreword: The Turk Street Mile”, in The China Governess: A Mystery, London: Chatto & Windus, →OCLC, page 15:

     A very neat old woman, still in her good outdoor coat and best beehive hat, was sitting at a polished mahogany table on whose surface there were several scored scratches so deep that a triangular piece of the veneer had come cleanly away, […].

2. Of, or pertaining to, triangles.
3. Having a triangle as a base; as, a triangular prism, a triangular pyramid.
4. Having three elements or parties; trilateral, tripartite.

• threeside, trigonal

Borrowed from Late Latin triangulāris.

• IPA^(key): (Central) [tɾi.əŋ.ɡuˈlar]
• IPA^(key): (Balearic) [tɾi.əŋ.ɡuˈla]
• IPA^(key): (Valencia) [tɾi.aŋ.ɡuˈlaɾ]

triangular m or f (masculine and feminine plural triangulars)

1. (geometry) triangular

From Latin triangulus +‎ -ar.

• IPA^(key): (Central, Balearic) [tɾi.əŋ.ɡuˈla]
• IPA^(key): (Valencia) [tɾi.aŋ.ɡuˈlaɾ]

triangular (first-person singular present triangulo, first-person singular preterite triangulí, past participle triangulat)

1. (transitive) to triangulate

• “triangular” in Diccionari català-valencià-balear, Antoni Maria Alcover and Francesc de Borja Moll, 1962.
• “triangular” in Diccionari normatiu valencià, Acadèmia Valenciana de la Llengua.
• “triangular”, in Gran Diccionari de la Llengua Catalana, Grup Enciclopèdia Catalana, 2026
• “triangular”, in Diccionari de la llengua catalana [Dictionary of the Catalan Language] (in Catalan), second edition, Institute of Catalan Studies [Catalan: Institut d'Estudis Catalans], April 2007

• Rhymes: -aɾ
• Hyphenation: trian‧gu‧lar

triangular m or f (plural triangulares)

1. triangular, shaped like a triangle
2. having a triangle as a base
3. having three elements or parties

• triángulo
• triangularmente

• “triangular”, in Dicionario da Real Academia Galega (in Galician), A Coruña: Royal Galician Academy, 2012–2026

Borrowed from Late Latin triangulāris.

• Hyphenation: tri‧an‧gu‧lar

triangular m or f (plural triangulares)

1. (geometry) triangular

• triângulo

From Latin triangulus +‎ -ar.

• Hyphenation: tri‧an‧gu‧lar

triangular (first-person singular present triangulo, first-person singular preterite triangulei, past participle triangulado)

1. (transitive) to triangulate

• “triangular”, in Dicionário Aulete Digital (in Portuguese), Rio de Janeiro: Lexikon Editora Digital, 2008–2026
• “triangular”, in Dicionário inFormal (in Portuguese), 2006–2026
• “triangular” in Dicionário Aberto based on Novo Diccionário da Língua Portuguesa de Cândido de Figueiredo, 1913
• “triangular”, in Dicionário infopédia da Lingua Portuguesa (in Portuguese), Porto: Porto Editora, 2003–2026
• “triangular”, in Michaelis Dicionário Brasileiro da Língua Portuguesa (in Portuguese), São Paulo: Editora Melhoramentos, 2015–2026, →ISBN
• “triangular”, in Dicionário Priberam da Língua Portuguesa (in Portuguese), Lisbon: Priberam, 2008–2026

Borrowed from French triangulaire.

triangular m or n (feminine singular triangulară, masculine plural triangulari, feminine/neuter plural triangulare)

1. triangular

• IPA^(key): /tɾjanɡuˈlaɾ/ [t̪ɾjãŋ.ɡuˈlaɾ]
• Rhymes: -aɾ
• Syllabification: trian‧gu‧lar

Borrowed from Late Latin triangulāris.

triangular m or f (masculine and feminine plural triangulares)

1. (geometry) triangular

From Latin triangulus +‎ -ar.

triangular (first-person singular present triangulo, first-person singular preterite triangulé, past participle triangulado)

1. (transitive) to triangulate

• “triangular”, in Diccionario de la lengua española [Dictionary of the Spanish Language] (in Spanish), online version 23.8.1, Royal Spanish Academy [Spanish: Real Academia Española], 15 December 2025