apart, not, away from
When something is diffuse, it is widely spread out and scattered.
Someone who is diffident is shy, does not want to draw notice to themselves, and is lacking in self-confidence.
If you are indifferent about something, you are uninterested or neutral about it, not caring either in a positive or negative way.
When you can differentiate between the people around you, you are able to distinguish or see the differences between them.
A difference in something is what makes it not like something else; it can also be a change that makes it not like it was before.
Differentiated vocabulary for your students is just a click away.