Which definition best applies to the term cultural assimilation?

1. the adoption of a brand new ideology by all groups within a society.
2. the adoption of elements of another society's culture in order to resist colonization
3. the adoption of the culture of a colonized people by a colonizer
4. the adoption by a smaller group of a larger group's beleifs, ides, and practicies

4. the adoption by a smaller group of a larger group's beliefs, ideas, and practices