Must/Have To/Have Got To

Must/Have To/Have Got To

Must and have to both express necessity:

--You must fill out this form. --You have to pick up Mr. Roberts.

In some situations, must is more urgent or stronger than have to:

--You must be here for your appointment on time. I have a busy schedule today. --You have to take another course next year.

The expression have got to is similar in meaning to must and have to but is reserved for spoken English:

--I have got to study more. (i.e., I must study more.)

Using May and Might

Two other important modal verbs are may and might. The two are used interchangeably in standard American English to express probability or possibility:

--You may be wrong. --You might be wrong. --The attorney might be late. --The attorney may be late.

The past form is expressed as follows:

modal (may/might) + have + past participle

--I may/might have left my glasses in the restaurant.

NOTE: Must can also be used to express probability:

--The plane must be leaving now.

Progressive Forms of May and Might

THE PAST PROGRESSIVE FORMS OF MAY AND MIGHT ARE FORMED BY ADDING HAVE BEEN + THE -ING FORM OF THE MAIN VERB.

--I didn't see them at the hotel. They may have been having dinner.

--The mail didn't arrive on time. The mailman might have been having trouble with his car.

THE PRESENT PROGRESSIVE FORMS OF MAY AND MIGHT ARE FORMED BY ADDING BE + THE -ING FORM OF THE MAIN VERB.

--We may be calling you in the morning.

--They might be visiting the U.S. this time next year. NOTE: When must means necessity, the past form is had to. When it means probability, the past is must have + past participle.

The Past Form of Should

To form the past of should simply add have + past participle:

--I missed my plane this morning. I should have left earlier.

--I can't find a hotel room. I should have made a reservation.

The past form of should conveys the notion of a failure or omission. Note that the customary pronunciation of should have is should've or shouda. The negative form is should not have, pronounced in colloquial English as shouldn't've or shouldn't'a.