You can type a plus or minus symbol on a Mac keyboard with just a few keystrokes. If you don't remember how to type a particular character on a Mac, you can often find it in the Emoji & Symbols menu accessible under Edit on the menu bar. If you're using a specialized programming or typesetting language like LaTeX or MathML, there are other ways to enter the plus or minus symbol.
Plus or Minus Sign
The plus or minus sign, ±, is used to indicate when a number should both be added and subtracted. It's sometimes used to express two quantities a+b and a-b as a±b and sometimes used to indicate a range of possibilities, such as n ± 10%.
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No matter how you intend to use the symbol, it's useful to know how to type it on your computer keyboard. How to do so varies from operating system to operating system. If you're using an Apple computer running macOS, type it on your Mac keyboard by holding down the "Option" and "Shift" keys and clicking the key with the equal and plus signs on the top row of keys. This shortcut places a plus or minus sign in your document, web browser input or other software.
Emoji & Symbols Menu
If you're ever unsure of how to type a particular symbol on your Mac, search for it in the Emoji & Symbols menu on macOS. Access this menu by clicking the "Edit" menu in any Mac program and then select "Emoji & Symbols." Scroll down to find the symbol you want or type to search for a symbol with a given name. The plus and minus sign is in the Math Symbols section.
Copy and Paste
If you have the symbol you want to use in one place on your computer, such as in an existing document or on an open web page, you may be able to copy it and paste it where you want it. Highlight the symbol, control-click or right-click, and select "Copy" in the pop-up menu.
When you put the cursor where you want the symbol, right-click or control-click again and click "Paste." If you don't have the symbol handy but want to use this method, search for it online.
Not Equal in LaTeX
If you use specialized software such as the LaTeX document preparation system, there may be a different way to generate a plus or minus sign. In LaTeX, for example, the symbol is written "\pm." In MathML, a system for writing math symbols, it is written "&PlusMinus."
Check the manual for any specialized mathematical software you use to find out how to represent the symbol correctly.