Unlock: Conjugate Priors

When the prior and likelihood are paired so the posterior stays in the same family as the prior. Definition via exponential families, the standard table (Beta-Bernoulli, Dirichlet-multinomial, Normal-Normal, Normal-inverse-gamma, Gamma-Poisson), worked Normal-Normal updates in 1D and the multivariate case, and the pseudo-observation interpretation that makes conjugacy a feature, not a coincidence.