1 Clearly, we recognize that the first sign functions as an order, while the second simply identifies. What enables us to interpret the signs is an interplay of linguistic and non-linguistic features. Grammatically, the word stop in the first sign could be a verb (in the imperative form) or a noun. Its location at the intersection of two streets (its context) suggests that it is more likely to be the verb ordering us to stop than the noun indicating a place where vehicles stop. In the second sign, however, stop is more likely to be a noun, because it is modified by another noun bus. Here, we are using the co-text (the surrounding text) to help make sense of the sign, along with the image of the bus itself. Thus, the function of the sign is an effect of the interplay between text, co-text and context – the context including the historical one of all our previous encounters with signs of this type.

2 a The signs function as an apology, a warning, a welcome, an invitation and a prohibition, respectively. At least three of the signs state their function explicitly: sorry, warning, welcome, while the other two have strong linguistic indicators of their purpose: please, no … . Even in the absence of any contextual information, it is easy to ‘read’ these signs.

b These signs, on the other hand, are less ‘transparent’, and even seem to be saying one thing while meaning another. The form of the first three is a present tense statement in each case – the semantic (i.e. literal) meaning being a fact (in the case of the first two) or a probability. They belong to the same family of statements as ‘The sun rises in the east’ or ‘It may rain’. In order to ‘read’ their purpose, we need to enlist the relevant contextual information that imbues these statements with some kind of communicative ‘force’ – their pragmatic meaning, in other words. Why would anyone display a statement about curbing dogs or feeding pigeons? Since we are used to interpreting public signage as often being ‘coercive’, and since we know that dog waste and rats are unhygienic, especially in the public contexts where the signs are situated, it is not difficult to read these signs as requests, even prohibitions: Please curb your dog; Do not feed the pigeons … . The ‘video surveillance’ sign requires a similar degree of contextual ‘unpacking’ in order to interpret its ‘warning’ sub-text. Finally, Thank you for not smoking appears, superficially, to have the function of thanking, but in fact is intended (and generally interpreted) as a prohibition.

‘Saying one thing but meaning another’ is what is called an indirect speech act, and is frequently motivated by the need to be polite – to avoid offending the person addressed by being too assertive.