pure imaginary number

8.8

A number equal to a real number not zero times i with no real part

noun

Specialized

: número imaginario puro

The number 3i is a pure imaginary number because its real part is zero.

Examples

She explained that multiplying two pure imaginary numbers yields a negative real number.
A pure imaginary number can be represented as bi.
In mathematics, a pure imaginary number is represented by a real multiple of i.
A pure imaginary number has no real component.
The number 3i is a pure imaginary number because its real part is zero.
In mathematics, a pure imaginary number is represented by a real multiple of i.
A pure imaginary number can be expressed in the form bi, where b is any nonzero real number.

Antonyms

real number

Specialized

9 3.9

A value that can be shown on a straight line, like 3, 1/2, or pi

Surface Forms

pure imaginary number singular

pure imaginary numbers plural

Morphology

pure + imaginary + number

The phrase is fully compositional: 'pure' (only/entirely) modifies 'imaginary number' so it literally means a number consisting solely of an imaginary part (no real component). Although precise understanding of 'imaginary' in the mathematical sense (the unit i and form bi) requires math background, the basic meaning is directly derivable from the constituent words.

Etymology

Pure imaginary number comes from a simple picture: imagine the usual numbers on a flat 'real' line and a second line going up from zero for 'imaginary' numbers. A pure imaginary number sits only on that up line, so its real part is 'zero' and it is a real number times 'i'.