 Especially in formal studies of syntax, morphology, etc., both terms are used to refer to utterances that draw from elements of two or more grammatical systems.These studies are often interested in the alignment of elements from distinct systems, or on constraints that limit switching.Some work defines code-mixing as the placing or mixing of various linguistic units (affixes, words, phrases, clauses) from two different grammatical systems within the same sentence and speech context, while code-switching is the placing or mixing of units (words, phrases, sentences) from two codes within the same speech context.