Question mark
The rhetorical question mark or percontation point was invented by Henry Denham in the 1580s and was used at the end of a rhetorical question; however, its use died out in the 17th century. It was later revived in modern-day society by Matt DiRoberto. It was the reverse of an ordinary question mark, so that instead of the main opening pointing back into the sentence, it opened away from it. This character can be represented using the reversed question mark (⸮) found in Unicode as U+2E2E. The percontation point is analogous to the irony mark, but those are even more rarely seen.
Diacritic
A diacritic – also diacritical mark, diacritical point, diacritical sign, or accent – is a glyph added to a letter, or basic glyph. The term derives from the Ancient Greek ("diakritikós", "distinguishing"), from ("diakrī́nō", "to distinguish"). "Diacritic" is primarily an adjective, though sometimes used as a noun, whereas "diacritical" is only ever an adjective. Some diacritical marks, such as the acute ( ´ ) and grave ( ` ), are often called "accents". Diacritical marks may appear above or below a letter, or in some other position such as within the letter or between two letters.