This is great app, just like bible of grammar.It has everything every English student need to learn about grammar. Tons of lessons on rules,examples and quizzes.

This is a false app. It is not free and the content is not perfect. I have noticed one GLARING error in just the free version. The free version only has the TO BE Verb. Why would I buy the full $20 version or smaller apps when I can see errors and the questions lack variety? When answering questions about the BE Verb, all answer choices were either IS or ARE, even though answer choices usually had HAVE and WERE as other choices. That's not even challenging or helpful.Here is an error example: "It______now a week since you left home. Choices: AREAMISWEREAnything wrong here?? IS is apparently the correct answer and the app gives the one sentence explanation: "It expresses state, third person singular hence "is." The correct answer is HAS BEEN - Present Perfect Tense. A vague or indeterminate time in the past that some how has meaning in present or asks about a recent past time in reference to the present. IS is correct if you don't know English or grammar rules or have learned bad English. In any case, you don't want to be learning from something that has wrong answers. When learning a LANGUAGE, answers should be PERFECT and detailed, accepting anything less will lead to problems and false understanding (especially in a static app that is not fast and riddled with errors like common spoken English). Conclusion: Waste of time and money.