In Modern Greek it is pronounced , (like the th in the English word this) but in the Ancient Greek language, it was pronounced .

A river delta is named after the letter delta because it has roughly the triangular shape of the upper-case delta.

The upper-case letter Δ is used as the symbol for:

• The difference operator, affecting a change or difference between mathematical values:

$\{y\_2-y\_1\backslash over\; x\_2-x\_1\}\; =\; \{\backslash Delta\; y\; \backslash over\; \backslash Delta\; x\}$ = the average change of y per unit x

• The Laplace operator:

$\backslash Delta\; f\; =\; \backslash frac\; \{\backslash partial^2\; f\}\{(\backslash partial\; x)^2\}\; +\; \backslash frac\; \{\backslash partial^2\; f\}\{(\backslash partial\; y)^2\}$

• The discriminant of the quadratic equation:

$\backslash Delta\; =\; b^2\; -\; 4ac\backslash ,\backslash !$

• A macroscopic change in the value of a variable in mathematics or science.
• Any of the delta particles in particle physics.
• As a symbol for defendant in legal shorthand.

The lower-case letter δ is used as the symbol for:

• An infinitesmal change in the value of a variable in mathematics or science.
• An auxiliary function in Calculus used to rigorously define the limit or continuity of a given function.
• The Kronecker delta in mathematics.
• The Dirac delta function in mathematics.
• Deflection in engineering mechanics
• A mark for deletion in proofreading. The usage is said to date back to classical times.

Greek letters

Δ | Delta (lizherenn) | Делта | Delta (lletra) | Delta | Delta (bogstav) | Delta | Δέλτα | Δ | Delta (greko) | دلتا | Delta | Deilte | Delta (letra) | Δ | Delta (lettera) | דלתא (אות) | Delta | Delta (letter) | Δ | Delta (bokstav) | Delta | Delta | Delta | Δ | Дельта (буква) | Delta | Delta | Delta | Delta | Δ