常用数学符号英文对照

Basic math symbols

Symbol	Symbol Name	Meaning / definition	图的同构 Example
=	equals sign	equality	5 = 2+3 5 is equal to 2+3
≠	not equal sign	inequality	5 ≠ 4 5 is not equal to 4
≈	approximately equal	approximation	sin(0.01) ≈ 0.01, x ≈ y means x is approximately equal to y
>	strict inequality	greater than	5 > 4 5 is greater than 4
<	strict inequality	less than	4 < 5 4 is less than 5
≥	inequality	greater than or equal to	5 ≥ 4, x ≥ y means x is greater than or equal to y
≤	inequality	less than or equal to	4 ≤ 5, x ≤ y means x is greater than or equal to y
( )	parentheses	calculate expression inside first	2 × (3+5) = 16
[ ]	brackets	calculate expression inside first	[(1+2)×(1+5)] = 18
+	plus sign	addition	1 + 1 = 2
−	minus sign	subtraction	2 − 1 = 1
±	plus - minus	both plus and minus operations	3 ± 5 = 8 and -2
±	minus - plus	both minus and plus operations	3 ± 5 = -2 and 8
*	asterisk	multiplication	2 * 3 = 6
×	times sign	multiplication	2 × 3 = 6
·	multiplication dot	multiplication	2 · 3 = 6
÷	division sign / obelus	division	6 ÷ 2 = 3
/	division slash	division	6 / 2 = 3
–	horizontal line	division / fraction

mod	modulo	remainder calculation	7 mod 2 = 1
.	period	decimal point, decimal separator	2.56 = 2+56/100
ab	power	exponent	23 = 8
a^b	caret	exponent	2 ^ 3 = 8
√a	square root	√a · √a = a	√9 = ±3
3√a	cube root	3√a · 3√a · 3√a = a	3√8 = 2
4√a	fourth root	4√a · 4√a · 4√a · 4√a = a	4√16 = ±2老年人手环
n√a	n-th root (radical)		for n=3, n√8 = 2
%	percent	1% = 1/100	10% × 30 = 3
‰	per-mille	1‰ = 1/1000 = 0.1%	10‰ × 30 = 0.3
ppm	中国新闻出版报 per-million	1ppm = 1/1000000	10ppm × 30 = 0.0003
ppb	per-billion	1ppb = 1/1000000000	10ppb × 30 = 3×10-7
ppt	per-trillion	1ppt = 10-12	10ppt × 30 = 3×10-10

Geometry symbols

Symbol	凌立如Symbol Name	Meaning / definition	Example
∠	angle	formed by two rays	∠ABC = 30°
	measured angle		ABC = 30°
	spherical angle		AOB = 30°
∟	right angle	= 90°	α = 90°
°	degree	1 turn = 360°	α = 60°
deg	degree	1 turn = 360deg	α = 60deg
′	prime	arcminute, 1° = 60′	α = 60°59′
″	double prime	arcsecond, 1′ = 60″	α = 60°59′59″
	line	infinite line
AB	line segment	line from point A to point B
荀子宥坐	ray	line that start from point A
	arc	arc from point A to point B	= 60°
⊥	perpendicular	perpendicular lines (90° angle)	AC ⊥ BC
\| \|	parallel	parallel lines	AB \| \| CD
≅	congruent to	equivalence of geometric shapes and size	∆ABC≅ ∆XYZ
~	similarity	same shapes, not same size	∆ABC~ ∆XYZ
Δ	triangle	triangle shape	ΔABC≅ ΔBCD
\|x-y\|	distance	distance between points x and y	\| x-y \| = 5
π	pi constant	π = is the ratio between the circumference and diameter of a circle	c = π·d = 2·π·r

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	y ∝ x when y = kx, k constant
∞	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	上海电气商和网 rounds number to lower integer	⌊4.3⌋ = 4
⌈x⌉	ceiling brackets	rounds number to upper integer	⌈4.3⌉ = 5
x!	exclamation mark	factorial	4! = 123*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)=x-1 ⇒(f ∘ g)(x)=3(x-1)

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