 The implicatures in  (1)  and  (2)  are conversational. They depend on features of the conversational context, and are not determined by the conventional meaning of the sentences uttered. A key feature in (1) was Alan’s question. Had he asked “What are you going to do today?”, Barb could have implicated something completely different (that she is going to work) by saying the same thing (that she has to work). Grice (1975: 25) contrasted a conversational implicature with a conventional implicature, by which he meant one that is determined by the meaning of the sentence  used.[7]  Here’s a variant of Grice’s example.