“Both mean ‘to put off to another day, to defer’. ‘Adjourn’ is from Latin ad and jurnus, a day. ‘Postpone’ is also from Latin post, after and ponars, place.
The meeting was adjourned.
Parliament adjourned last week and will meet again after four weeks.

Postpone’ is used both in formal and informal contexts.
I have postponed my trip to Calcutta.
Why don’t you postpone the meeting to next week?

'Adjourn’ has another meaning besides the one I have already mentioned. It means ‘to move to another place’.
After dinner, they adjourned to the lawn.

'Postpone’ does not have this meaning. You can postpone your trip but you cannot postpone to another room. ‘Postpone’ also means ‘to place after in order of importance’.
You must postpone private profit to the public welfare.

It means you must subordinate your private interests to the public welfare. In other words, your interests should occupy a subordinate position. The word ‘adjourn’ is not used in this sense at all.”