Ξξ
MATHEMATICS
- Variable/index (ξ).
- Appears in PDEs and special functions.
PROBABILITY
- Random variable (ξ) in some texts.
- Parameter in stochastic models (convention).
STATISTICS
- Sometimes used for latent observations/noise.
- Depends on author convention.
PRONUNCIATION
- Ancient Greek
- sound [ks]
- Modern Greek
- ξι [ksi] · sound [ks]
HOW TO WRITE IT — click to copy
lowercase
uppercase
DON'T CONFUSE IT
- ζ ξ ς γ ζ has a single turn before the tail; ξ has two; ς is the final sigma.
- ξ ζ ε ς ξ has two turns stacked before the tail — like a 3 with a tail; ζ has only one.
Note: notations vary between books/fields; these are the most common usages.