Why are the articles different in these pairs of sentences?
1a) We had breakfast at 8 o’clock.
b) The breakfast on the train was awful.
2a) We left in the afternoon.
b) We left at night.
3a) We travelled by train.
b) We came on the early train.
4a) the Himalayas
b) Mont Blanc
5a) the United States
6a) the London road
b) London Road
7a) The telephone is a great invention.
b) Mobile phones are a nuisance.
PDF for easy saving and printing: differences between articles