Synonyms Lessons containing synonyms enable a program accepting more than one correct solution via text input. If a synonym is not stored in the lesson, the user can complete the lesson via immediate synonym extension. During a game, the user input is backdated to be a correct solution after adding the synonym. Typing Error Tolerance A program tolerant against typing errors corrects small errors automatically, requests the user when detecting a medium error and assumes the user not to know the solution if he really typed an other word only. The threshold between typing error and wrong answer is continuously adjustable.
Some programs allow substitutes, e.g. using an a for an .
Lesson Editors Compacting Compacting is a function of a lesson editor, which removes all double entries of a lesson and combines their synonym lists. Concatenation A lesson editor can concatenate two lessons. Mirror Capability of a lesson editor to mirror the languages of a lesson.