The Greek letters are very important and most commonly used in Mathematical formulae. In recent days, Hebrew letters have also engaged a very good position among notational characters in Modern Mathematics.

Letters LaTex code
\alpha \alpha
\beta \beta
\chi \chi
\delta \delta
\epsilon \epsilon
\eta \eta
\gamma \gamma
\iota \iota
\kappa \kappa
\lambda \lambda
\mu \mu
\nu \nu
o o
\omega \omega
\phi \phi
\pi \pi
\psi \psi
\rho \rho
\sigma \sigma
\tau \tau
\theta \theta
\upsilon \upsilon
\xi \xi
\zeta \zeta
\digamma \digamma
\varepsilon \varepsilon
\varkappa \varkappa
\varphi \varphi
\varpi \varpi
\varrho \varrho
\varsigma \varsigma
\vartheta \vartheta
\Delta \Delta
\Gamma \Gamma
\Lambda \Lambda
\Omega \Omega
\Phi \Phi
\Pi \Pi
\Psi \Psi
\Sigma \Sigma
\Theta \Theta
\Upsilon \Upsilon
\Xi \Xi
\aleph \aleph
\beth \beth
\daleth \daleth
\gimel \gimel

Remember that when writting LaTeX cases are very important. For example $latex \delta$ renders \delta, however $latex \Delta$ renders \Delta.