Basic shapes are fundamendal PDFs, with often well-known functional form. They are usually fully analytically implemented and often a thin wrapper around Distribution. Any missing shape can be easily wrapped using WrapDistribution.

zfit.pdf.Gauss(mu, sigma, obs, *[, ...])	Gaussian or Normal distribution with a mean (mu) and a standartdeviation (sigma).
zfit.pdf.Exponential([lam, obs, extended, ...])	Exponential function exp(lambda * x).
zfit.pdf.CrystalBall(mu, sigma, alpha, n, obs, *)	Crystal Ball shaped PDF.
zfit.pdf.DoubleCB(mu, sigma, alphal, nl, ...)	Double-sided Crystal Ball shaped PDF.
zfit.pdf.GeneralizedCB(mu, sigmal, alphal, ...)	Generalized asymmetric double-sided Crystal Ball shaped PDF.
zfit.pdf.GaussExpTail(mu, sigma, alpha, obs, *)	GaussExpTail shaped PDF.
zfit.pdf.GeneralizedGaussExpTail(mu, sigmal, ...)	GeneralizedGaussedExpTail shaped PDF which is Generalized assymetric double-sided GaussExpTail shaped PDF.
zfit.pdf.Uniform(low, high, obs, *[, ...])	Uniform distribution which is constant between low, high and zero outside.
zfit.pdf.Cauchy(m, gamma, obs, *[, ...])	Non-relativistic Breit-Wigner (Cauchy) PDF representing the energy distribution of a decaying particle.
zfit.pdf.Voigt(m, sigma, gamma[, obs, ...])	Voigt profile.
zfit.pdf.TruncatedGauss(mu, sigma, low, ...)	Gaussian distribution that is 0 outside of low, high.
zfit.pdf.BifurGauss(mu, sigmal, sigmar, obs, *)	Bifurcated Gaussian distribution different standard deviations for the left and right side of the mean.
zfit.pdf.Poisson([lam, obs, extended, norm, ...])	Poisson distribution, parametrized with an event rate parameter (lamb).
zfit.pdf.LogNormal(mu, sigma, obs, *[, ...])	Log-normal distribution, the exponential of a normal distribution.
zfit.pdf.QGauss(q, mu, sigma, obs, *[, ...])	Q-Gaussian distribution with parameter q.
zfit.pdf.ChiSquared(ndof, obs, *[, ...])	ChiSquared distribution for ndof degrees of freedom.
zfit.pdf.StudentT(ndof, mu, sigma, obs[, ...])	StudentT distribution for ndof degrees of freedom.
zfit.pdf.Gamma(gamma, beta, mu, obs, *[, ...])	Gamma distribution.
zfit.pdf.JohnsonSU(mu, lambd, gamma, delta, ...)	Johnson's SU distribution.