No hyphen is needed for world class. World is just an adjective that describes class much like (for example) upper class, which also does not need a hyphen.
As with many compound terms, it depends on the usage and placement. In general, if the words are used as a modifier directly preceding the modified word, the hyphen is required. Otherwise the hyphen is not used. Examples: * "We use only first-class ingredients." * "Your presentation was first class." Style manuals such as Words into Type and Chicago Book of Stylehave chapters detailing hyphen usage, and they're excellent references for any writer or student.
As with many compound terms, it depends on the usage and placement. In general, if the words are used as a modifier directly preceding the modified word, the hyphen is required. Otherwise the hyphen is not used. Examples: * "We use only first-class ingredients." * "Your presentation was first class." Style manuals such as Words into Type and Chicago Book of Stylehave chapters detailing hyphen usage, and they're excellent references for any writer or student.
No
The dictionaries that list it use a hyphen.
Yes, in this case "seventh-grade class" should have a hyphen to show that the words "seventh" and "grade" are functioning as a single adjective modifying the noun "class."
No, excitingly is one word so you would not use a hyphen in it.
You do not use a hyphen when writing square feet. Using a hyphen would make it one word which should not be the case.
It isn't in the dictionary, so it'd be best to use a hyphen.
no
Yes, whenver using square-foot you should use a hyphen
It's not a word in the dictionary, so yes, use the hyphen.