Things HAVE or HAS Changed? Which is correct?

“Things Have Changed” is correct because “things” is plural and therefore conjugates with “have”. You would say “something has changed” because something is singular.

Can’t you see that everything is different now? Things have changed.

Something has changed about your face. Did you get a haircut? 

What tense is “Has/Have changed”?

Has and Have changed are examples of the Present Perfect Simple. You can read more about how to use the present perfect here. 

Has Changed or Had changed?

“Has Changed” is the present perfect simple and “had changed” is the past perfect simple. We use the present perfect simple to show that something happened in the past and it had an effect on the present whereas we use the past perfect simple when we want to show that something happened before another time in the past. 

Have Changed or Have Been Changed?

“Have Changed” is the present perfect simple in the active voice whereas “Have Been Changed” is the present perfect simple in the passive voice. The difference is that in the passive voice we don’t know (or don’t care) who the main subject is in the sentence. You can read more about the passive voice in my complete guide here. 

Have Changed or Was Changed?

“Have Changed” is the present perfect simple and “was changed” is the past simple form of this phrase in the passive voice.

Conor