There is agreement across different approaches that although sentences consist of words, they are much more than strings of words: They also have structure. Section 1 shows how clause structure is analysed very differently across different approaches. The rest of the paper addresses ambiguity: lexical ambiguity in section 2, morphological structural ambiguity in section 3, and syntactic structural ambiguity in section 4. Subsections 4.1-4.2 analyse the ambiguity arising when a constituent, e.g. a PP, is interpretable either as the sister of one constituent or of another constituent. Subsection 4.3 argues that the ambiguous examples analysed in all of section 4 cannot be accounted for within approaches that do not recognise a constituent that contains a verb and its complement (i.e. a VP).