The public mood changed dramatically after the bombing.

[Edwalker]

Hello.

The following sentences are from the Cambridge Learners Dictionary under the entry for "After".

The public mood changed dramatically after the bombing.
After further discussion, we decided to call the police.

In the first sentence, the word "after" is listed as a preposition. In the second, it is listed as a conjunction. I do not understand the difference, given that "the bombing" and "further discussion" are both noun phrases. Is it because the second example implies a verb (after holding further discussion, ...)? I am also unsure about this sentence from a college resource:

After our trip to the beach, school started back, and I was excited to see my friends.

This is described as a compound-complex sentence in the workbook which means, I think, that "After" has to be a coordinating conjunction here. Again, I don't understand why the the noun phrase "our trip to the beach" is enough for this first part to constitute a clause rather than a phrase. Is it to do with the implication of a verb (after we took our trip to the beach, ...)?

Thank you for any help you can offer.
Ed

 

[jutfrank]

It's a preposition in all three cases because it's followed by a noun phrase.

 

[Edwalker]

It's a preposition in all three cases because it's followed by a noun phrase.

Thank you.

So the following is actually a compound sentence?

After our trip to the beach, school started back, and I was excited to see my friends.