This applications helps you to classify Japanese verbs into transitive verbs (他動詞, literally "other move words") and intransitive verbs (自動詞, literally "self move words). For example, in
ドアが開きます。(akimasu) The door opens.
ドアを開けます。(akemasu) (Someone) opens the door.
"開きます" is an intransitive verb and what opens is indicated through "が". "開けます" is a transitive verb and what is being opened is indicated through "を". You need to understand the difference between the two "opens" to form a correct sentence.
Difficulties are:
- In English, the difference between transitive and intransitive words is not as explicit as in other languages. The verb is just "to open". In German, the intransitive version is "sich öffnen", the transitive is just "öffnen".
- There are a few rules in Japanese, but many cases that you just have to learn.
- But most learning resources are in English. For example, you can train the meaning of a verb with Wanikani and you can see if it's transitive or intransitive, but you cannot currently train the verb class.
To use the app, please visit: ... Note that you need a Wanikani account (not yet, but you will).
Disclaimer: I am not a language expert, just a learner trying to solve a problem.