The necessity modals have to, must, need to, and should

When an ambiguous lexical item appears within a familiar string of words, it can instantly receive an appropriate interpretation from this context, thus being saturated by it. Such a context may also short-circuit illocutionary and other pragmatic aspects of interpretation. We here extract from the British National Corpus over 500 internally highly collocating and high-frequency lexical n-grams up to 5 words containing have to, must, need to, and/or should. These contexts-as-constructions go some way toward allowing us to group these four necessity modals into clusters with similar semantic and pragmatic properties and to determine which of them is semantico-pragmatically most unlike the others. It appears that have to and need to cluster most closely together thanks to their shared environments (e.g., you may have/need to…, expressing contingent, mitigated necessity), while should has the largest share of unique n-grams (e.g., rhetorical Why shouldn’t I…?, used as a defiant self-exhortation).