Factor analysis (also known as common factor analysis and exploratory factor analysis) seeks to describe a collection of observed variables in terms of a smaller collection of (unobservable) latent variables, or factors. These factors, which are defined as linear combinations of the observed variables, are constructed to explain variation that is common to the observed variables. A primary goal of factor analysis is to achieve a meaningful interpretation of the observed variables through the factors. Another goal is to reduce the number of variables.