To ascertain the boundaries of the various units of a phrase or clause, a linguist looks for appropriate syntactic tests. Ambiguity Phrases and clauses may be either lexically or structurally ambiguous. Tree diagrams are useful because they can disambiguate ambiguous sentences. The man who hunts ducks out on weekends. The cotton clothing is usually made of grows in Mississippi.
Fat people eat accumulates.
Join elements that belong to the same phrase, working from right to left. Label the phrases. Continue joining and labeling items until you reach the top of the tree. The syntactic structures and the order of the elements vary from language to language. Phrase structure rules specify the constituency of syntactic categories in the language.