imaginary number
noun
: a complex number (such as 2 + 3i) in which the coefficient of the imaginary unit is not zero
called also imaginary
compare pure imaginaryExamples of imaginary number in a Sentence
Recent Examples on the Web
Then, in 2021, the role of imaginary numbers in quantum theory attracted newfound interest.
—
Daniel Garisto, Quanta Magazine, 7 Nov. 2025
There are also what are known as imaginary numbers like i, which is the square root of –1, and complex numbers, which are sums of real and imaginary numbers.
—Kenneth Chang, New York Times, 26 Mar. 2025
This means they are made of both real numbers and the imaginary number i: the square root of negative 1.
—William Ross, The Conversation, 10 Mar. 2025
Other rings of integers can be built out of sets of numbers that include, say, the square root of −1 (the imaginary number that mathematicians call i), or the cube root of 2.
—Joseph Howlett, WIRED, 9 Mar. 2025
There’s imaginary numbers and abstract theoretical math.
—The Editors, JSTOR Daily, 24 Jan. 2024
Eventually, the parts of the photon’s behavior described by the imaginary numbers will correspond to actual measurable properties.
—Jackie Appel, Popular Mechanics, 10 June 2023
Examples are automatically compiled from online sources to
show current usage.
Read More
Opinions expressed in the examples do not represent those of Merriam-Webster or its editors.
Send us feedback.
Daniel Garisto, Quanta Magazine, 7 Nov. 2025
There are also what are known as imaginary numbers like i, which is the square root of –1, and complex numbers, which are sums of real and imaginary numbers.
—Kenneth Chang, New York Times, 26 Mar. 2025
This means they are made of both real numbers and the imaginary number i: the square root of negative 1.
—William Ross, The Conversation, 10 Mar. 2025
Other rings of integers can be built out of sets of numbers that include, say, the square root of −1 (the imaginary number that mathematicians call i), or the cube root of 2.
—Joseph Howlett, WIRED, 9 Mar. 2025
There’s imaginary numbers and abstract theoretical math.
—The Editors, JSTOR Daily, 24 Jan. 2024
Eventually, the parts of the photon’s behavior described by the imaginary numbers will correspond to actual measurable properties.
—Jackie Appel, Popular Mechanics, 10 June 2023
Cite this Entry
“Imaginary number.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/imaginary%20number. Accessed 29 Nov. 2025.
Copy CitationLove words? Need even more definitions?
Merriam-Webster unabridged
Share