Formal and functional similarities in a learner's first and second languages (L1 and L2) facilitate the perception of cross-linguistic equivalence between individual items (phonemes, morphemes, words, and phrases). The beginning foreign language learner makes frequent use of these perceived equivalences when he learns to understand L2 items. This receptive competence in turn creates a basis for development of productive competence. Cross-linguistic similarities alone may not directly facilitate the mastery of L2 systems for use in production, but the learner who can easily perceive cross-linguistic equivalences will easily build a basic receptive competence that can be converted into productive competence. Furthermore, although the L2 learner whose L1 is a related language may have problems with minimally distinct patterns and other factors, he will probably make fewer errors that seriously affect communication than the learner whose L1 and L2 are not related. (MSE)