Meanings Of The Modal Verbs II.
Must : Can express necessity: There must be some mistake. The speaker judges the proposition to be necessarily true. The speaker drawn conclusions from things already known. There is also a root necessity meaning of must: To be healthy, a plant must receive moisture and sunshine. where must has a meaning of essentiality.
Obligation or complusion: You must be back by ten o’clock. The speaker is advocating a certain form of behaviour. The speaker is exercising his authority. Exception when the subject is in first person. I must remember to write. The speaker in this case exercises authority over himself. Ocassionaly must occurs with negations. His absence must not have been noticed. The occurence is rare in questions. Must there be a good reason for…. This assumes a positive answer. Some case MUST has sarcastic use with a 2nd person subject: If you must smoke, at least….
Need, have(got) to: Need is used as the negative and question form of must in root senses: Need they make all that noise. Have(got) to can also be substituted for must with little or no difference in meaning. In the case of logical necessity have(got) to is more emphatic than must and used mostly in AmE. In the obligation sense have(got) to is felt more impersonal than must. It is noticable with a firs person subject: I’m afraid I have to go now. Where must implies self obligation, have(got) to implies obligation by external forces. Since must has no past and nonfinite form, have to in many contexts where must is impossible.(when following a modal verb: We’ll have to be patient.)
Ought to and should: Where they contrast with must and have to is that they are not expressing the speakers confidence in the occurance of the event or state described. There is tentative interference where the speaker is not sure about that his statement is true but tentatively concludes that it is true on the basis that he knows. Should and ought to differ from must in that they frequently refer to the future. The job should be finished by next Monday.
Obligation: Ought and should do not imply that the speaker has confidence that the recommendation will be carried out. In the perfective aspect they have the meaning that the recommendation has not been carried out. They should have met her at the station.
Will/would: Where shall end should is not interchangeable with will and would the contraction( ‘ll ‘d) does not substitute for shall and should though it can for will and would. When in the predictive sense the change to shall is not possible then the contraction to ‘ll is possible.
Prediction: There are three related uses:
1. The common future predictive sense of will and the prediction in the past sense of would: I was told I would feel better after this medicine.
2. The present predictive sense of will which is rare and is similar in meaning to must in logical necessity sense: She will have had her dinner by now.
3. The habitual predictive meaning often occurs in conditionals:
If you eat salty you will get thirsty. Or it occurs in descriptions of personal habit or behaviour.
He’ll talk for hours if you let him. In past tense narratives would can describe habitual behaviour:
In the spring the birds would return to their old haunts.
1. Intention: I will write as soon as I can.
2. Willingness: Will you help me to..
3. Insistence: If you will go out without your overcoat, what can you expect.