I'm wondering about the distinction between expressions like "high performance" and "high-performance", or "high level" and "high-level" and other similar pairs of words which are sometimes used with a hyphen and sometimes not.
Am I right that without the hyphen, the first word is an adjective and the second a noun, whereas with the hyphen, the pair should be used as an adjective and would need a noun to go with it? Also, am I right that some expressions, such as "high-performance computing" have an established meaning and are usually used with a hyphen?
- High-performance is often desired ... (incorrect use)
- High performance is often desired ... (correct use)
- High-performance computing is ... (correct use)
- High performance computing is ... (correct use but not following established norm)