Sigma (Σ, σ)
Quick Info
- Pronunciation: SIG-muh
- English: s
- Common Use: Sum, Standard deviation
Historical Background
Eighteenth letter of the Greek alphabet, derived from Phoenician letter "shin", meaning teeth. The symbol Σ has been used since ancient times to represent summation in mathematics, while σ is fundamental in statistics as the symbol for standard deviation.
Scientific Applications
Mathematics
Summation
Statistics
Standard deviation
Physics
Surface charge density
Materials Science
Stress
Chemistry
Molecular bonding
Symbol Codes
Unicode
Uppercase
- Code: U+03A3
- Hex: Σ
- Decimal: Σ
Lowercase
- Code: U+03C3
- Hex: σ
- Decimal: σ
HTML
Uppercase
Σ
HTML entity for uppercase Sigma
Lowercase
σ
HTML entity for lowercase sigma
LaTeX
Uppercase
\Sigma
LaTeX command for uppercase Sigma
Lowercase
\sigma
LaTeX command for lowercase sigma
Common Usage
Mathematics
Series
Summation of sequences
Set Theory
Algebraic structures
Linear Algebra
Matrix operations
Statistics
Descriptive Statistics
Standard deviation
Inferential Statistics
Population variance
Data Analysis
Dispersion measures
Physics
Electrostatics
Surface charge density
Mechanics
Normal stress
Thermodynamics
Stefan-Boltzmann constant
Common Applications
Statistics
Population variance
Sample standard deviation
Z-score calculation
Series and Sequences
Basel problem
Binomial expansion
Geometric series
Special Applications
Engineering Stress
Hooke's law
Yield stress
Ultimate stress
Statistical Analysis
Confidence interval
Empirical rule
Standard error
Summation Properties
Basic Properties
Linearity
Constant sum
Sum of integers
Advanced Properties
Sum of squares
Double sum
Binomial sum
Physical Applications
Materials Science
- • Stress analysis
- • Material strength
- • Deformation studies
- • Failure criteria
Statistical Physics
- • Ensemble averages
- • Fluctuation theory
- • Distribution functions
- • Partition functions
Quantum Mechanics
- • Spin states
- • Orbital notation
- • Selection rules
- • Coupling schemes
Theoretical Applications
Series Theory
Riemann zeta function
Taylor series
Geometric series
Statistical Theory
Variance definition
Variance addition
Coefficient of variation
Writing Guidelines
Uppercase is a three-barred symbol (Σ) used for summation, lowercase looks like a curved o with a tail (σ). Note that there are two forms of lowercase sigma: σ (final form) and ς (word-end form). In handwriting, ensure the lowercase σ is clearly distinguished from the Latin o and the Greek omicron (ο).
How to Type Sigma
Windows
Alt Code
- Hold Alt
- Type 931 for Σ or 963 for σ
- Release Alt
Character Map
- Open Character Map
- Select Greek
- Find and copy Sigma
Unicode
- Hold Alt + X
- Type 03A3 for Σ or 03C3 for σ
- Release Alt + X
macOS
Option Key
- Press Option + w for σ
Character Viewer
- Press Control + Command + Space
- Select Greek
- Click Sigma
Linux
Compose Key
- Press Compose + s + s for σ
Unicode
- Press Ctrl + Shift + U
- Type 03C3
- Press Enter
Frequently Asked Questions
What is the difference between Σ and ∑?
While both symbols represent summation, Σ is the Greek letter Sigma, while ∑ is the mathematical summation symbol. In practice, they are often used interchangeably in mathematical notation.
Why are there two forms of lowercase sigma (σ and ς)?
In Greek writing, ς (final sigma) is used when sigma appears at the end of a word, while σ is used in all other positions. In mathematical and scientific notation, σ is the standard form used regardless of position.
How is sigma used in statistics?
In statistics, σ (sigma) represents the standard deviation of a population, measuring the spread of data around the mean. The squared version, σ², represents variance.
What's the difference between σ and s in statistics?
σ (sigma) represents the population standard deviation, while s represents the sample standard deviation. σ is a parameter, while s is a statistic calculated from sample data.