complex number

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any number of the form a + bi, where a and b are real numbers and i is an imaginary number whose square equals −1.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun complex analysis A number of the form a + bi, where a and b are real numbers and i denotes the imaginary unit

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun (mathematics) a number of the form a+bi where a and b are real numbers and i is the square root of -1