The rules of grammar that we "learn" are an attempt to model a process that we don't understand very well. It's hard to say that grammar defines a language when

The rules of grammar that we "learn" are an attempt to model a process that we don't understand very well. It's hard to say that grammar defines a language when a speaker/writer can at will break any rule and enhance their communication by creating new constructions and vocabulary on the fly. Rules are at best a simple description of some expectations. Context, observation, and additional communication can completely override any rule. Grammers are useful in communication, but they certainly don't define and constrain it; they are like standardization in tool making and manufacturing. But words combined together, in a context, can behave in ways that no grammar can describe. In fact I'd say that grammars are more conscriptive than they are descriptive. Literacy and education teach us to speak and write in grammars for formal, ritual use. But when we need to get work done or communicate important ideas, anything goes...