A | $\alpha$ | alpha | I | $\iota$ | iota | P | $\rho$ | rho |

B | $\beta$ | beta | K | $\kappa$ | kappa | $\mathrm\Sigma$ | $\sigma$ | sigma |

$\mathrm\Gamma$ | $\gamma$ | gamma | $\mathrm\Lambda$ | $\lambda$ | lambda | T | $\tau$ | tau |

$\mathrm\Delta$ | $\delta$ | delta | M | $\mu$ | mu | Y | $\upsilon$ | upsilon |

E | $\epsilon$ | epsilon | N | $\nu$ | nu | $\mathrm\Phi$ | $\phi$ | phi |

Z | $\zeta$ | zeta | $\mathrm\Xi$ | $\xi$ | xi | X | $\chi$ | chi |

H | $\eta$ | eta | O | o | omicron | $\mathrm\Psi$ | $\psi$ | psi |

$\mathrm\Theta$ | $\theta$ | theta | $\mathrm\Pi$ | $\pi$ | pi | $\mathrm\Omega$ | $\omega$ | omega |

Epsilon may also be written as $\varepsilon$, kappa as $\varkappa$, theta as $\vartheta$, and phi as $\varphi$.

$\alpha$, $\beta$, and $\gamma$

These Greek letters are often used to label the three angles in a triangle (Chapter 10: Geometry).

Delta often represents a change, especially in calculus (Section 15.3.1: Instantaneous Rate of Change).

It can also represent the Laplace operator, or the discriminant of a quadratic equation (Section 7.5.5: Quadratic Equations).

Epsilon often represents some small, positive number, especially in ‘epsilon-delta’ proofs (Question 9.6.6).

These letters are often used for labelling angles, especially when using polar coordinates (Section 11.5: Polar Coordinates).

Phi is also the symbol for the golden ratio (Question 7.5.30).

Mu is used for the SI prefix ‘micro’, which means $10^{-6}$ (Section a.3.1: SI Prefixes).

Pi is the ratio of a circle’s circumference to its area (Section 10.7.1: Circumference).

Capital Pi and Sigma represent the product and sum of a sequence (Section 7.7: Sequences).

In physics, angular frequency ($2\pi\times$ the frequency) is often given the variable name $\omega$.

This is the symbol for the Ohm, a unit of resistance (Section a.1.2: Derived Units).