Level 8 - Mail 12

[Prof. Guillermo Katz]

Dear students:

 

Next subject is modals.  Enclosed is some additional information about this.

 

See you in class!

 

Gmo

 

MODAL VERBS

 

	ABILITY
		For an ability in the present we can use CAN or BE ABLE TO. There is no difference in meaning but CAN is more common.
		She can play the piano.
		For an ability in the past we can use COULD or WAS/WERE ABLE TO. There is a difference in meaning:
		(a)	COULD is used for a general ability in the past       She could play the piano when she was six.
		(b)	WAS/WERE ABLE TO is used for a particular ability in the past       I didn't forget my keys so we were able to unlock the door.
		(c)	COULD can be used for a particular ability in the past when the sentence is negated, or when the lexical verb is a verb of perception       I forgot my keys so we weren't able to/couldn't unlock the door.
		CAN and COULD do not have non-finite forms (infinitive, -ing or participles) so they cannot we used in tenses or constructions that require those forms. Instead we have to use BE ABLE TO
		You will be able to speak fluent Englsih in a few years.

 

	PERMISSION
		To ask for permission we may use CAN (more common, more direct), COULD (more common, less direct, more polite), MAY (more formal), or MIGHT (more formal, less direct).
		Can she play your piano? Could I use your phone? May I erase the blackboard? Might I make a suggestion?
		To give permission we may use CAN (more common, more direct),or MAY (more common, less direct, more polite)
		Can she play your piano? Yes, she can. Could I use your phone? Of course you can. May I erase the blackboard? No, you can't. Might I make a suggestion? No, you may not.
		To TALK ABOUT having permission we may use CAN, COULD or BE ALLOWED TO
		(a)	We use CAN or AM/ARE ALLOWED TO to talk about a permission we have in the present
			The children are allowed to/can stay up late on Saturdays.
		(b)	We use COULD or WAS/WERE ALLOWED TO to talk about a general permission we had in the past
			We were allowed to/could stay up late on Saturdays.
		(c)	To talk about a particular permission we had in the past we use  WAS/WERE ALLOWED TO
			We were allowed to stay up late last Saturday.

 

	OBLIGATION AND NECESSITY
		To express an obligation or necessity for an action in the present or the future we can use MUST or HAVE TO. There is a difference in meaning:
		(a)	MUST is used when the authority comes from the speaker       You must eat your vegetables, I insist.
		(b)	HAVE TO is used when the authority comes from outside the speaker      You have to eat your vegetables. The doctor said you need more vitamins.
		MUST does not have a past tense or non-finite forms (infinitive, -ing or participles) so it cannot we used in tenses or constructions that require those forms. Instead we have to use HAVE TO
		Peter had to speak with his teacher after his exams.
		To say that it is obligatory or necessary NOT TO DO something we  use MUST NOT (MUSTN'T)
		You mustn't eat that plant. It is poisonous.
		To say that it is NOT obligatory or necessary to do something we  use DON'T HAVE TO, NEEDN'T or DON'T NEED TO
		You don't have to eat your vegetables. Leave them if you want. You don't need to come if you'd rather stay at home.
		To say that something was NOT obligatory or necessary in the past we  use NEEDN'T HAVE + past participle or DIDN'T NEED TO + infinitive.There is a difference in meaning.
		(a)	NEEDN'T HAVE indicates that something was not necessary or obligatory but that it happened anyways.
			You needn't have come. You could have stayed at home.
		(b)	DIDN'T NEED TO only indicates that something was not necessary or obligatory (we do not know whether it happened or not)
			You didn't need to come to class yesterday. Did any of you come?

See you in class!  Gmo