Please tell me if the following sentences are the same or not?
It is ten o’clock. They must have arrived now.
It is ten o’clock. They must have arrived by now.
Are they same? If not, then please tell me what the difference between them is.
Learn English – “They must have arrived now” vs. “They must have arrived by now”
grammarprepositionsword-usage
Best Answer
They mean different things about a possible event in a past interval that extends to the present time. The first is an inference from evidence. Suppose you're awaiting guests and you hear a commotion in the hallway outside your door. You say, "They must have arrived now", meaning that the noise indicates that your guests are here.
The second is more speculative and concerns a deadline. Suppose your friends are traveling by train, and their train is scheduled to arrive in the station at 1:00PM. When it's 1:15PM and you say, "They must have arrived by now", you mean that it's reasonable to conclude that your friends are at the station because the scheduled arrival time has passed. You don't actually know that, of course. The train might be late or your friends might have failed to make the train at its departure.
Note that neither of these usages expresses an aspect of compulsion as when your friends actually arrive at your apartment and you tell them "You must take your shoes off before you enter."