consistent hyphenation

[JeffBezanson]

For some reason I am not too good at this. Specifically run time and dynamically typed appear both with and without hyphens.

[jiahao]

Google n-grams data:

You're welcome.

[JeffBezanson]

Thanks.

I wonder if there is a difference between "at run time" and "the runtime system".

[jiahao]

The OED defines "run time" as execution time:

run time n. Computing the time at or during which a program or other task runs (often contrasted to the time at or during which a program is compiled); the length of time taken by the execution of a program or task.

(The OED lists 4 examples of usage; two are hyphenated and the other two are not.)

I would consider 'runtime' to refer to the system, e.g. "The Julia runtime is a library."

[jiahao]

Wikipedia claims that both 'run-time system' and 'runtime system' are acceptable spellings. The former hyphenation looks like a disambiguating hyphen - run-time system = system at (run time) as opposed to run of (time system), long-range order = order at (long range) as opposed to long (range order).

[JeffBezanson]

Ok, I think I'll adopt "runtime system" and "at run time".

[alanedelman]

Cool. I always wonder about semicircle vs semi-circle

[StefanKarpinski]

For what it's worth, I have the same problem. Worsened by the analogy with "compile time" – and clearly "compiletime" is not a word :-\

[jiahao]

Consider: "compile time", but "compile-time semantics".

[stevengj]

The guideline is that you hyphenate compound adjectives, not nouns. "At run time" is using "run time" as a noun phrase, hence no hyphen. "run-time compilation" is using "run time" as a compound adjective modifying "compilation", and hence it is good style (at least in many style guides) to hyphenate it as an indication of associativity: "run" modifies "time", and together "run-time" modifies "compilation".

When a compound becomes common enough, sometimes people begin to elide the hyphen, e.g. "run-time compilation" becomes "runtime compilation", or "every-day prices" becomes "everyday prices". I think the main thing is to pick a widespread spelling and stick with it consistently.

Some style guides suggest hyphenating compounds only when there is some ambiguity, but I prefer to just consistently hyphenate compound adjectives. There is (at least) one exception: almost all style guides recommend that you never hyphenate compounds using an adverb ending in "ly", such as "easily baked desserts" (there is never any parsing ambiguity in this case, because an adverb can only modify the adjective, not the noun).

[jiahao]

Also, "data flow analysis".