I walk over the hilltop and see a dog with a cast on its leg running around. We supply context if it is not given. First, as the great Russian linguist Voloshinov pointed out, language is learned in social interaction. Meaning is social in that it is acquired and exercised in social relationships, and all messages have a relational component. Second, language has meaning only as it means, roughly, the same thing to a community of people.
Meaning exists only as shared meaning.
The point of any sign system is that it communicates, that is, means the same thing to a number of people. Signs only work as parts of systems of signs, having relationships of similarity and difference from each other. We say, then , that the signs are coded. Unless we can see the salient similarities and differences among any set of signs, whether they are sets of words or styles of architecture or the covers of paperback novels or hand signals, and unless we can interpret their meaning, we can't 'read' the code. Any code set will have significant relationship to any other code set, will 'fit in' to the practices and world view in some way.