The basic idea of latent semantic analysis (LSA) is, that
text do have a higher order (=latent semantic) structure which,
however, is obscured by word usage (e.g. through the use of
synonyms or polysemy). By using conceptual indices that are
derived statistically via a truncated singular value
decomposition (a two-mode factor analysis) over a given
document-term matrix, this variability problem can be overcome.