One of the use of would has been listed below:
You use would , or would have with a past participle, to indicate that you are assuming or guessing that something is true, because you have good reasons for thinking it.
⇒ You wouldn't know him.
⇒ His fans would already be familiar with Caroline.
⇒ That would have been Della's car.
⇒ He made a promise to his great-grandfather? That would have been a long time ago.
⇒ It was half seven; her mother would be annoyed because he was so late.
Source :http://www.collinsdictionary.com/dictionary/english/would
What I'm most confused(not understood) is as follows:
Use of would is just like the use of 'must' for drawing logical conclusion or presumption: for example:
*His fans would already be familar with caroline.
You mustn't know him.That must have been Della's car.
So, how would is different from 'must' in this usage ?
I would appreciate your helpful responses.Thank you.
Best Answer
In grammar, the idea of modality is to express subjective attitudes and opinions of the speaker about a possibility, probability, necessity, obligation, permission, ability, desire, and contingency.
All these categories can be ranked by the degree from high to low, where must refers to the former and would — to the latter. In other words, must asserts what we conclude to be the most likely interpretation of a situation or events, and would — a less likely one.
Cut to the chase, compared with would, must expresses a higher degree of probability and means "I'm sure", "I'm most certain", "most probably" whereas would means "I suppose/assume", "probably", "maybe", "I should think".
To refer to the past, we use would with the perfect infinitive:
P.S. Should you want to have modal verbs listed by their modality strength approximately, here you are:
You should bear in mind that the idea of modality can also be expressed through nouns, adjectives and adverbs: