Editing Imaginary unit (section)

== Terminology ==
{{Further|Complex number#History}}
Square roots of negative numbers are called ''imaginary'' because in [[History of mathematics#Renaissance|early-modern mathematics]], only what are now called [[real numbers]], obtainable by physical measurements or basic arithmetic, were considered to be numbers at all – even [[negative numbers]] were treated with skepticism – so the square root of a negative number was previously considered undefined or nonsensical. The name ''imaginary'' is generally credited to [[René Descartes]], and [[Isaac Newton]] used the term as early as 1670.<ref>{{cite journal|title=The New Language of Mathematics |last=Silver |first=Daniel S.|journal=[[American Scientist]] |volume=105 |number=6 |date=November–December 2017 |pages=364–371 |doi=10.1511/2017.105.6.364 |url=https://www.americanscientist.org/article/the-new-language-of-mathematics}}</ref><ref>{{cite OED|imaginary number}}</ref> The {{mvar|i}} notation was introduced by [[Leonhard Euler]].<ref name=Boyer>{{cite book|title = A History of Mathematics|last1 = Boyer|first1 = Carl B.|author-link=Carl Benjamin Boyer|last2 = Merzbach |first2=Uta C.|author2-link = Uta Merzbach|publisher = [[John Wiley & Sons]]|isbn = 978-0-471-54397-8|pages = [https://archive.org/details/historyofmathema00boye/page/439 439–445]|year = 1991|url = https://archive.org/details/historyofmathema00boye/page/439}}</ref>

A ''unit'' is an undivided whole, and ''unity'' or the ''unit number'' is the number [[1|one]] ({{math|1}}).