Punctual means arriving at the exact time agreed, not five minutes after it. The person already sitting down with a notebook open when you walk in at two.
Punctual fits people and services as a standing habit: a punctual student, a punctual bus service. For one single occasion English reaches for on time instead — the train was on time sounds right, the train was punctual sounds stiff. The noun is punctuality, and it is what employers file under reliability. Punctually pairs with a stated hour: the ceremony began punctually at eleven. There is no common one-word opposite; late does the job.
1adjectivepunctualArriving or happening at exactly the time agreed.
“He is punctual to the minute, which makes waiting for everyone else painful.”
Also accepted in games: on time
Punctual comes from Medieval Latin pūnctuālis, 'relating to a point', built on Latin pūnctus, 'point'. A punctual person hits the point — the exact mark on the clock face, not the area around it.
Latin
pūnctus — point
Medieval Latin
pūnctuālis — relating to a point
English, today
punctual
Medieval Latin pūnctuālis (“relating to a point”), from Latin pūnctus (“point”) + -ālis.
Etymology from Wiktionary, CC BY-SA