Lambda in LaTeX (\lambda)

Where it is used

Lowercase Greek lambda, used for eigenvalues, wavelengths, rates, and regularization strength.

Linear algebra writes Av = \lambda v for an eigenvalue and eigenvector. Physics uses \lambda for wavelength in c = \lambda f, probability uses it for the rate of a Poisson or exponential distribution, and optimization uses it for Lagrange multipliers and the penalty weight in ridge or lasso, \lambda\|w\|^2. Computer science writes anonymous functions with lambda calculus, \lambda x.\, x + 1. Its uppercase \Lambda is a separate command with different uses. Learning-rate schedules and exponential smoothing also borrow \lambda for decay factors.

Also listed under: Linear Algebra, Physics, Optimization

Minimal compilable example

Paste this into an empty .tex file and compile it with pdfLaTeX, XeLaTeX or LuaLaTeX.

\documentclass{article}
\begin{document}
Lambda: $\lambda$

\[ A\mathbf{v} = \lambda \mathbf{v}, \quad \det(A - \lambda I) = 0 \]
\end{document}

Related symbols

• Lambda (Upper)\Lambda
• Kappa\kappa
• Mu\mu
• Iota\iota
• Nu\nu
• Theta (Upper)\Theta

Frequently asked questions

How do I write Lambda in LaTeX?

Type \lambda in math mode, for example $A\mathbf{v} = \lambda \mathbf{v}, \quad \det(A - \lambda I) = 0$. It works in plain LaTeX without loading any package.

Which package do I need for \lambda?

None. \lambda is part of standard LaTeX, so it compiles with nothing in the preamble but the document class.

Can I use \lambda in text mode, or only in math mode?

Only in math mode. Outside $...$ LaTeX stops with "Missing $ inserted", so write $\lambda$ in running text. If you only need the glyph in text, paste the Unicode character λ instead (with XeLaTeX or LuaLaTeX and a font that has it).