Kinds of Adjective Clause

1. Who = used for people as Subject
   
2. Whom = used for people as Object
3. Which = used for things
4. That = used for both people and things
   
5. Whose = used for Possessive Pronoun (usually modifies people, but it may also be used to modify things)
6. Where/in which = used for place
   
7. When/ on which = used in an adjective clause to modify a noun of time (year, day, time, century, etc.)
8. Why = used for the reason