Math Symbols

Date: 03/11/2002 at 20:40:54
From: Marisol
Subject: Symbols

What do these symbols mean?

 ~ ! @ # $ % ^ & * ( ) - _ + = / ?

I know what some are used for, but I don't know what they mean.

Date: 03/11/2002 at 22:35:50
From: Doctor Twe
Subject: Re: Symbols

Hi Marisol - thanks for writing to Dr. Math.

Like letters of the alphabet, symbols have different meanings in 
different contexts or situations. I'll give you some meanings of your 
symbols in mathematical contexts.

~  This symbol is called a tilde. In symbolic logic (a field of math 
used a lot in computer sciences) it is used to denote "not." For 
example, ~A means "not A." In some other contexts, it means 
"approximately." For example, pi ~= 3.1416. (Note that sometimes it is 
written above the equal sign, and sometimes it is used without an 
equal sign - it depends on the situation and the publisher.)

!  The factorial of an integer is the product of all integers below it 
down to one. For example, 4! = 4 x 3 x 2 x 1 = 24.

@  The "at sign." This symbol generally means "at" or "each." For 
example, dr.math@mathforum.org is read as "doctor math at math forum 
dot org," while "3 pears, $.40 @" is read as "three pears, 40 cents 
each."

#  The name of this symbol is the octothorpe (most people don't know 
this). It is commonly called the "pound sign" or the "number sign" 
because that is what it is generally used to represent. 24# is read 
as "24 pounds," while "fax #: 1-800-555-1212" is read as "fax number 
1-800-555-1212."

$  The dollar sign. This usually is used to represent currency; U.S. 
dollars, Canadian dollars, etc.

%  The percent sign. Percent means "per 100" or "divided by 100." When 
following a number, it indicates that the number is a percentage. For 
example, 25% = 25 per 100 = 25/100 = 1/4 or .25.

^  The carat. In math, particularly when typing on a keyboard, this 
symbol can be used to indicate raised to a power. For example, 
4^3 = 4 to the 3rd power = 4 x 4 x 4 = 64. 

&  This symbol is called an ampersand. It almost always means "and," 
both in and outside of mathematics.

*  This symbol is called an asterisk. In mathematics, we sometimes use 
it to mean multiplication, particularly with computers. For example, 
5*3 = 5 times 3 = 15.

()  The open (or left) and close (or right) parenthesis. In math, 
operations enclosed in parentheses must be done before operations 
outside of parentheses. Parentheses are almost always used as a 
pair.

-  The hyphen, sometimes called a dash. In math, it usually means 
subtraction. For example 5-3 = 5 minus 3 = 2. 

_  The underscore. This is sometimes used to indicate a base or 
subscript (especially when typing on a keyboard). For example 1001_2 
means 1001 base 2 or 1001 with a subscripted 2.

+  The plus sign. In arithmetic, it means addition. For example, 
5+3 = 8. In symbolic logic, it is used to represent "or." For example, 
A+B is read as "A or B." 

=  The equals sign. This is one of several symbols that can be used to 
mean equals or equivalence. Some fields of math make a distinction 
between equal and equivalent, and use different symbols for each.

/  The forward slash. Often used when typing on a keyboard to 
represent division. For example, 8/2 = 4. 

I hope this helps! If you have any more questions, write back!

- Doctor TWE, The Math Forum
  http://mathforum.org/dr.math/