Is the following sentence correct?
No sooner had she hung up the phone than it rang again.
I really have difficulty with this sentence. I can not understand whether it is correct or not and the meaning of the sentence.
Let's have a look at the sentence:
"No sooner had she hung up the phone than it rang again."
'No sooner' is an adverbial comparative, which is why it requires a 'than' clause after it. I think the structure is clearer in the equivalent (and equally correct) non-inverted form:
"She had <no sooner> hung up the phone <than> it rang again."
It is plainer here that 'no sooner' is an adverb modifying the phrasal verb 'to hang up'. The verb is in the past perfect tense ('had' + past participle) because it refers to a past event that is earlier in time than another past event - 'it (the phone) rang again'.
So, without the comparative, the sentence would be:
"She had hung up the phone, and (then) it rang again."
In other words, a past perfect event followed (at some unspecified time) by a past simple event.
The addition of 'no sooner...than...' modifies this sentence to mean the past simple event occurred IMMEDIATELY after the past perfect event. It does this in a rather strange way by saying that the act of the phone ringing again did not occur 'later than' she had hung it up. Obviously, the two tenses used, and the context, tell us that this cannot be true - she must have hung up the phone before it rang again. But the expression is implying that the two events are so close in time that you could ALMOST say that one did not occur before the other.