Later vs after
I read the rule " Usage of "After" Adverb: Later than someone or something else: Hilary got here at midday and Nicholas arrived soon after. I can't go next week - how about the week after (= the following week)?"
So, I wrote "We sat down on the beach. It started to rain five minutes AFTER" ( Later than someone or something else). I looked at the key and it appeared I made a mistake - I should say "We sat down on the beach. It started to rain five minutes LATER."
Could you please explain the rule used in this case? Why do I have to use "Later" not "After" in the case above?

Thank you!!

Question

Later vs after
I read the rule " Usage of "After" Adverb: Later than someone or something else: Hilary got here at midday and Nicholas arrived soon after. I can't go next week - how about the week after (= the following week)?"
So, I wrote "We sat down on the beach. It started to rain five minutes AFTER" ( Later than someone or something else). I looked at the key and it appeared I made a mistake - I should say "We sat down on the beach. It started to rain five minutes LATER."
Could you please explain the rule used in this case? Why do I have to use "Later" not "After" in the case above?

Thank you!!

Answer

The question is "after what?"  Remember that "after" is also a preposition.

"The week after" is taken as a fixed phrase.  So is "soon after". In both of your examples, we have a given time so we can understand these phrases to mean "after next week" and "soon after midday." In short, we are not repeating the time reference which would usually follow "after", so the meaning is clear.

Yes, you should have written "five minutes later", because "it rained five minutes after" makes me ask, "After what? Where's the time reference?" We have missing information.