 Terms from other grammatical categories, as well, might admit a rigid/non-rigid distinction (for the broadest account of rigidity available, see Haze 2021). Philosophers have attended relatively little to the status of verbs and adverbs, in this connection (but see, e.g., López de Sa 2008). Compare ‘to begin writing’, ‘to commence writing’, and ‘to do what the teacher commanded at time t’ (where the command was, “Begin writing”). Evidently, the necessity of ‘One is about to begin writing if and only if one is about to commence writing’ is not enjoyed by ‘One is about to begin writing if and only if one is about to do what the teacher commanded at time t’. Arguably, the reason for the modal differences has to do with the rigidity or non-rigidity, in some appropriately extended sense, of the contained verbs. Something similar applies to adverbs. Compare ‘She ran quickly’ with ‘She ran in the manner signaled by her coach’ (where the signal means: Run quickly!). 