Suspend is to temporarily stop (stop temporarily) an activity/event that is currently happening.
Examples:
All children were suspended from school due to the COVID19 pandemic breakout. (which means all children had been in the school before the pandemic, and they had to go their home temporarily)
Due to the outbreak of the new crown epidemic, the children have suspended classes (the children have been attending classes in school before and were forced to stop)
The meeting was suspended because of lunch time.
The meeting was temporarily stopped.
Postpone is to move a planned activity/event that has not yet happened to a later date, which means it is in-purpose (purpose) and reasonable (reasonable) action, and this action is initiated (initiated) by someone who has enough power to Delay an existing plan.
Examples:
The All-Employee Meeting is posted to next week due to due to the accidental absence of company GM.
The absence of the company's general manager has led to the postponement of the entire employee meeting until next week.
My boss decided to postpone the project deadline due to the unexpected longer lead time of the key equipment.
Because the delivery period of the key equipment was too much beyond expectations, my boss decided to postpone the acceptance date of the project.
Defer also is to move a planned event to a later date in purpose, but it carries more negative connotation(negative).
Example:
The meeting was deferred to next Wednesday.
Delay is a period of time before an event happens. It can be used widely, but it can’t carry voluntary (voluntary) (in purpose) connotation (meaning), because Delay is unpredictable.
Examples:
I was delayed for the morning meeting because of heavy traffic on the way.
In the morning, the traffic jam on the road to work was severe, which delayed the morning meeting (the meeting did not stop because of my lateness)