imaginary unit

noun

An imaginary number (in the case of complex numbers, usually denoted i) that is defined as a solution to the equation x²=-1.

Meanings

nounimaginary unit (plural imaginary units)

plural imaginary units

  1. quaternion theorycomplex analysisAn imaginary number (in the case of complex numbers, usually denoted i) that is defined as a solution to the equation x²=-1.
    3 more examples

    In Section 4.3 we introduced the imaginary unit i with (i)²#61;-1, in the complex space domain. In section 4.4 we introduced the complex unit j with (j)²#61;-1, in connection with the time dependency of the shape (4.4.16) of the swimming profile. These different imaginary units have no interaction, we leave unaltered the product ij.

    2013, J. A. Sparenberg, Hydrodynamic Propulsion and Its Optimization, Springer, page 183

    2014, Dennis G. Zill, Warren S. Wright, Advanced Engineering Mathematics, Ascend Learning (Jones & Bartlett Learning), 5th Edition, page 793, We now simply say that i is the imaginary unit and define it by the property i²=-1. Using the imaginary unit, we build a general complex number out of two real numbers.

    Consider now in addition to the given #92;H#92;subset#92;mathbb#123;O#125;, one of the totally imaginary units not contained in #92;H, and note that #123;SU#125;(2) acts transitively on the set of totally imaginary units of a quaternion algebra; as we are assuming #92;alpha#92;notin#92;H, we may in fact assume that #92;mathbb#123;O#125;#61;#92;H#92;oplus#92;H' with #92;alpha#92;in#92;H'.

    2021, Bruce Hunt, Locally Mixed Symmetric Spaces, Springer, page 123

Origin

So named because it takes on the role of unit for the imaginary part of a complex number.

Full word history & related roots →

Translations

Finnish imaginaariyksikkö
  • imaginaariyksikköimaginary number
French unité imaginaire
  • unité imaginaireimaginary number
German imaginäre Einheit
  • imaginäre Einheitimaginary number
Hindi अधिकल्पित एकक
  • अधिकल्पित एकक (adhikalpit ekak)imaginary number
Italian unità immaginaria
  • unità immaginariaimaginary number
Japanese 虚数単位
  • 虚数単位 (kyosū tan'i)imaginary number
Korean 허수단위
  • 허수단위 (heosudanwi)imaginary number
Latin unitas imaginaria
  • unitas imaginariaimaginary number
Polish jednostka urojona
  • jednostka urojonaimaginary number
Russian мни́мая едини́ца
  • мни́мая едини́ца (mnímaja jediníca)imaginary number
Thai หน่วยจินตภาพ
  • หน่วยจินตภาพ (nùai-jin-dtà-pâap)imaginary number
Cite this entry
APA

imaginary unit. (n.d.). In WatkinsX Dictionary. Retrieved November 3, 2026, from https://dictionary.watkinsx.com/word/imaginary%20unit

MLA

“imaginary unit.” WatkinsX Dictionary, https://dictionary.watkinsx.com/word/imaginary%20unit. Accessed November 3, 2026.

Chicago

WatkinsX Dictionary, s.v. “imaginary unit,” accessed November 3, 2026, https://dictionary.watkinsx.com/word/imaginary%20unit.

Source: imaginary unit on Wiktionary, CC BY-SA 4.0.