Algebra symbols 
Symbol 
Symbol Name 
Meaning / definition 
Example 
x 
x variable 
unknown value to find 
when 2x = 4, then
x = 2 
≡ 
equivalence 
identical to 

≜ 
equal by definition 
equal by definition 

:= 
equal by definition 
equal by definition 

~ 
approximately equal 
weak approximation 
11 ~ 10 
≈ 
approximately equal 
approximation 
sin(0.01) ≈ 0.01 
∝ 
proportional to 
proportional to 
f(x)
∝ g(x) 
∞ 
lemniscate 
infinity symbol 

≪ 
much less than 
much less than 
1
≪ 1000000 
≫ 
much greater than 
much greater than 
1000000
≫ 1 
( ) 
parentheses 
calculate expression inside first 
2 * (3+5) = 16 
[ ] 
brackets 
calculate expression inside first 
[(1+2)*(1+5)] = 18 
{ } 
braces 
set 

⌊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 
fractional 
4! = 1*2*3*4 = 24 
 x  
single vertical bar 
absolute value 
 5  = 5 
f (x) 
function of x 
maps values of x to f(x) 
f (x) = 3x+5 
(f
∘g) 
function composition 
(f
∘g) (x) = f (g(x)) 
f (x)=3x,
g(x)=x1
⇒(f
∘g)(x)=3(x1) 
(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→∞ 
γ 
EulerMascheroni
constant 
γ = 0.527721566... 

φ 
golden ratio 
golden ratio constant 

π 
pi constant 
π = 3.141592654...
is the ratio between the
circumference and diameter of a circle 
c = π·d = 2·π·r 