Hyphens, En Dashes, Em Dashes

Q. I need to know the difference between a soft and hard hyphen in regard to proofing marks. Can you please help me out? Thank you kindly.

A. A hard hyphen is one that is typed deliberately and that must remain whether the phrase falls at the end of a line or in the middle of a sentence. An example is the hyphen in “two-thirds.” A soft hyphen, on the other hand, is there only when a word must be broken at the end of a line; it has likely been inserted by a word-processing feature, and it should disappear if the word falls in the middle of a sentence during typesetting. An example is “care-fully.” If you are preparing a manuscript for typesetting, there should be no soft hyphens in it, and if you notice one on the printed manuscript, you should mark it out (see fig. 2.5 in CMOS). If your word-processing program has an automatic hyphenation feature, it should be turned off.