The Babylonian mathematicians are the main cause for the origin of algebra several thousands years ago. The term algebra is it defines the numbers to be represented as variables . Algebra is classified into two categories;
They are,
Ancient algebra and
Modern algebra.
Ancient algebra mainly deals with elementary level of solving problems which involves basic arithmetic operations only. Algebra mostly consists of letters and symbols. Each letter and symbol has certain meanings. In this article we are going to see about algebra letters and meanings.
The word algebra means the branch of math that deals with the numbers denoted as letters or alphabets of English alphabets.
For example a number in general can be represented by `n` . The most common value or letter used in algebra is `x` .The area is denoted by `A` , volume is denoted by `V` , length is denoted by `l` , width is denoted by `w` , height is denoted by `h` , radius is denoted by `r` , time is denoted as `t` or `T` , base of a 3  dimensional object is `b` ,area of triangle is denoted by `Delta` ,side is denoted by `s` etc.
Here are some letters and their meanings in algebra:
Symbol 
Symbol Name 
Meaning/ definition 
Example 
x, y 
x and y variable 
unknown value to find 
when 3x = 6, then x = 2 
≡ 
equivalence 
identical to 
x ≡ y 
≜ 
equal by definition 
equal by definition 
x≜y 
~ 
approximately equal 
weak approximation 
11 ~ 10 
≈ 
approximately equal 
approximation 
sin(0.01) ≈ 0.01 
∝ 
proportional to 
proportional to 
f(x) ∝ g(x) 
∞ 
lemniscates 
infinity symbol 
x<=∞ 
≪ 
much less than 
much less than 
1 ≪ 1000000 
≫ 
much greater than 
much greater than 
1000000 ≫ 1 
( ) 
parentheses 
calculate expression inside first 
3 * (4+6) = 30 
[ ] 
brackets 
calculate expression inside first 
[(1+2)*(1+5)] = 18 
{ } 
braces 
set 
{2,3,4,5} 
⌊x⌋ 
floor brackets 
rounds number to lower integer 
⌊4.3⌋= 4 
⌈x⌉ 
ceiling brackets 
rounds number to upper integer 
⌈4.3⌉= 5 
x! 
exclamation mark 
factorial 
3! = 1*2*3 = 6 
f (x) 
function of x 
maps values of x to f(x) 
f (x) = 3x+5 
(a,b) 
open interval 
(a,b) ≜ {x  a < x < b} 
x ∈ (2,6) 
[a,b] 
closed interval 
[a,b] ≜ {x  a ≤ x ≤ b} 
x ∈ [2,6] 
∆ 
delta 
change / difference 
∆t = t_{1}  t_{0} 
∆ 
discriminant 
Δ = b^{2}  4ac 

∑ 
sigma 
summation  sum of all values in range of series 
∑ x_{i}= x_{1}+x_{2}+...+x_{n} 
∑∑ 
sigma 
double summation 

∏ 
capital pi 
product  product of all values in range of series 
∏ x_{i}=x_{1}∙x_{2}∙...∙x_{n} 
e 
e constant / Euler's number 
e = 2.718281828... 
.e = lim (1+1/x)^{x} , x→∞ 
Symbol 
Symbol Name 
Meaning/ definition 
Example 
+ 
Plus 
Addition of numbers 
2 + 3 = 5 
 
Minus 
Subtraction of numbers 
3 – 2 = 1 
X 
Product 
Multiplication of numbers 
5 x 4 = 20 
/ 
Division 
Divide the numbers 
`10/2` = 5 
= 
Equal 
Equal to 
2 = 2 
≠ 
Not equal to 
The given equation is not equal 
X + 5 ≠ x + 3 
± 
Plus or minus 
Both positive and negative numbers 
Sqrt 16 = ± 4 
`alpha` 
alpha 
Alpha value 
x <= `alpha` 
`beta` 
beta 
Beta value 
y>= `beta` 
`theta` 
theta 
Used to represent degree of angle 
`theta` = 45 degree 
`sigma` 
sigma 
Sigma value 
`sigma =sum(fd^2)/N` 
`__` 
perpendicular 
Perpendicular line 
`angle A__angleB` 