I’m not sure if I mentioned this in class or not, but there are a couple of conventional symbols used to indicate the grammatical status of example sentences. I wanted to find this out there somewhere on the web, but my searches didn’t reveal much. The best I found was a writeup about “asterisk” on everything2.com but that doesn’t seem like a very definitive source.

In any event, the basic distinction is between no marking (grammatical) and being marked with an asterisk or “star” (ungrammatical).

However, judgments often do not feel that clear-cut, so this is sometimes expressed with the help of question marks. I have even seen cases of people using more than one star (**), presumably to indicate something like “gut-wrenching ungrammaticality.”

One question mark (?) is “dubious” or “marginal”, two question marks (??) is worse, a question mark and a star is still worse (?*), but all are better than flat-out ungrammatical (*).

How you actually treat an example with, say, a ?? grammaticality rating winds up depending a bit on what is being discussed. Sometimes people will take ?? examples to be better than you’d expect, hence something that the grammar should generate, and sometimes people will consider them to be worse than they should be, hence something that the grammar should not generate. It’s a bit of a grey area.

You might also see the hash mark (#), which is usually used to indicate a sentence that is grammatical in principle, but either nonsensical or inappropriate in a discourse. So, to use a well-worn example (that was also mentioned in class), #My toothbrush is pregnant again. Or, in response to the question “Who bought the lamp?” the answer “#Pat bought THE LAMP” (an answer that would have been perfectly fine as a response to the question “What did Pat buy?”).

There is also a notational shorthand that people often use to compare two (or more) sentences, one of which is grammatical and the other of which isn’t. When a sentence would be rendered ungrammatical by adding a word, the two sentences can be written together with the added word in parentheses (indicating optionality), and with a star inside the parentheses (indicating that if you take the option to add the word, the result is ungrammatical: Pat ate (*quickly) the apple. This is shorthand for the two sentences “Pat ate the apple” (grammatical) and “*Pat ate quickly the apple” (ungrammatical). A bit weirder is the case where not taking the option results in ungrammaticality, which is indicated by a star outside the parentheses: Pat ate the *(apple). This is shorthand for “Pat ate the apple” (grammatical) and “*Pat ate the” (ungrammatical). A simple parenthesized string, without adornment, means that both sentences (with and without the parenthesized material) are grammatical: Pat ate the apple (quickly). I’ll mention this parenthesis notation in class too.