The Diu Indo-Portuguese negator admits two forms, namely nã (often reduced to nə) and the emphatic form nãw. The former is highly dominant in clausal negation, while the latter is almost entirely reserved for propositional negation (i.e. as an interjection negating entire propositions, used for instance to answer polar questions). The crucial difference between the two is one of clausal embedding. Whereas the emphatic form is a stand-alone form, the reduced form integrates the structure of a clause. Consider the distribution of nãw and nə in Example 169 (which is the reply to a question demanding whether or not the interlocutor was scared of cockroaches).
Source: Cardoso 2009: 209
Source: Cardoso 2009: 210
Source: Cardoso 2009: 210