reasonI frankly don’t understand the reason for the delay.
causeInvestigators have not yet determined the cause of the fire.
rootWe need to get to the root of her problems.
motiveThere seems to have been no motive for the murder.
ground(s)On what grounds was she dismissed?
purposeCan I ask what the purpose of this meeting is?
excuseHe said his car broke down, but it was just an excuse.
pretextShe stayed at home on the pretext of having lots of work to do.