Lambda (Λ λ) in LaTeX
In LaTeX, \lambda gives the lowercase lambda (λ) and \Lambda gives the uppercase lambda (Λ), both used in maths mode.
LaTeX command
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Lowercase lambda, \lambda, is one of the most heavily used Greek letters. In linear algebra it is the eigenvalue in A\mathbf{v} = \lambda \mathbf{v}; in physics it is a wavelength; in probability it is the rate of a Poisson or exponential distribution; and in optimisation it is a Lagrange multiplier or a regularisation strength. It also names the anonymous functions of lambda calculus.
Uppercase lambda, \Lambda, is a triangle-like symbol. In cosmology it is the cosmological constant, giving the Lambda-CDM model its name; in particle physics it labels the Lambda baryon; and in mathematics it can denote a lattice or a diagonal matrix of eigenvalues. Type \Lambda for the capital.
Both commands are maths-mode only; lowercase \lambda is italic and uppercase \Lambda upright by default. There is no \varlambda variant. For a bold lambda use \boldsymbol{\lambda}; for an upright roman lambda, rare as a unit or constant, the upgreek package provides \uplambda in a full document.
Other forms
\lambdalowercase lambda\Lambdauppercase lambda (Λ)Examples
$\lambda$lowercase lambda inline
$A\mathbf{v} = \lambda \mathbf{v}$the eigenvalue equation
$P(X=k) = \frac{\lambda^k e^{-\lambda}}{k!}$the Poisson distribution with rate lambda
$\det(A - \lambda I) = 0$the characteristic equation
$\Lambda$uppercase lambda
Tips and common mistakes
- Use
\lambdafor eigenvalues, wavelengths and rates;\Lambdafor the cosmological constant or a diagonal eigenvalue matrix. - There is no
\varlambdavariant; only\lambdaand\Lambdaexist. - For a bold lambda use
\boldsymbol{\lambda}, since\mathbfdoes not bold lowercase Greek letters. - Lambda commands require maths mode; wrap them in .
- In regularised regression lambda is the penalty weight, as in a ridge term
\lambda \lVertw\rVert^2.
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Convert your maths to LaTeX →FAQ
How do I write a capital lambda in LaTeX?
Use \Lambda, which renders Λ. It commonly denotes the cosmological constant or a diagonal matrix of eigenvalues.
Is there a variant lambda like \vartheta?
No. Lambda has only \lambda and \Lambda; there is no \varlambda in standard LaTeX or KaTeX.
How do I write the eigenvalue lambda?
Write the eigenvalue equation as and the characteristic equation as .