nouns - "Runtime", "run time", and "run-time"

The CLR under .NET is referred to as the "Common Language Runtime." It seems that the convention is "runtime" for a noun and "run-time" for the adjective. Is this correct or should it be "runtime" also? I'm inclined to think it should be like the following:

1. The variable is typed at runtime.



2. The runtime variable is null.

Answer

I (as a programmer and linguist) would pretty much always use runtime.

I think you might be building too much into the idea that runtime is an 'adjective' in compounds such as runtime environment. The word still remains more noun-like than adjective-like[*] in such cases and there's little motivation for inventing a special spelling in that case. And if you look at examples of actual articles, textbooks etc, I think you'll find most authors come to the same conclusion.

In the Java and C# APIs, I also don't think you'll find a case of it being spelt "RunTime" rather than "Runtime".

[*] cf. "more flexible environment"~"*more runtime environment"; "this environment is flexible"~"*this environment is runtime" etc. These aren't perfect tests, because "adjective" vs "noun" don't really constitute a perfect dichotomy. But you can see that "runtime" is more at the 'nouny' than the 'adjectivy' end of the scale in these cases.