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.
Interrogative
Another common way of marking questions is with the use of a grammatical particle or an enclitic, to turn a statement into a yes–no question enquiring whether that statement is true. A particle may be placed at the beginning or end of the sentence, or attached to an element within the sentence. Examples of interrogative particles typically placed at the start of the sentence include the French "est-ce que" and Polish "czy". (The English word "whether" behaves in this way too, but is used in indirect questions only.) The constructed language Esperanto uses the particle "ĉu", which operates like the Polish "czy":