Likelihood (eikos, versimilis) captures the idea that something is likely to happen or to have happened. As a formal concept, it has appeared in jurisprudence, commerce and scholasticism long before it was given a rigorous mathematical foundation.[1]

Likelihood function

Main article: Likelihood function

Likelihood is a function of how likely an event is, which is weaker than probability (or odds in favor).

In statistics, a likelihood function is a function of the parameters of a statistical model, defined as follows: the likelihood of a set of parameter values given some observed outcomes is equal to the probability of those observed outcomes given those parameter values. Likelihood functions play a key role in statistical inference, especially methods of estimating a parameter using a statistics (a function of the data).