Subjunctive Cases of a Verb

12. When is a verb put into the subjunctive case?
A verb is put into the subjunctive case if it follows one of the four following prepositions:

ﺃن لن ﺇذن کی

For example:
1) ﺃریدُ ﺃن ﺃتعلّمَ النَحو (I want to learn syntax.)

2) لَن یَجودَ البَخیلُ (A miser will not be generous.)

3) ﺇذَن نُنزلَکَ فی دارِنا (In that case, we will let you stay in our house.)

4) ﺃدرُس کَی تَحفَظَ (Study so that you preserve.)