Syntagm is a linguistic term that refers to a group of words that function together as a unit. Some synonyms for this concept include phrase, sentence, clause, and expression. These terms all describe different levels of syntactic units that can be found in language. A phrase is a group of words that work together, but don't contain a subject and a predicate. A sentence is a complete thought, containing a subject and a predicate. A clause is a group of words that contains both a subject and a predicate but doesn't express a complete thought. Finally, an expression is a phrase or sentence that can be interpreted figuratively or idiomatically. These synonyms can be used interchangeably in the field of linguistics to describe different aspects of language structure.