Auxiliary verbs and their equivalents

Be able to instead of can

Be able to often has the same meaning as can.

  • He can walk on his hands. OR He is able to walk on his hands.
  • I am unable to understand his motive. OR I can’t understand his motive.
  • They were able to catch the thief. OR They could catch the thief.

Be to instead of will or shall

The structure be + to can be used to express simple futurity.

  • He is to retire next year. = He will retire next year.
  • The President is to visit Japan next month. = The President will visit Japan next month.
  • We are to get a wage rise in June. = We will get a wage rise in June.

Be + to instead of must

The structure be + to is also used to give orders. In this case, it means almost like must.

  • You are to complete the work in two days. (= You must complete the work in two days.)
  • He is to report for duty within a week.

Had better instead of should or ought to

  • You had better consult a good doctor. = You should consult a good doctor.

Had better may also express a threat.

  • He had better be careful.

Have to instead of must

  • I have to be there at 10 o’clock. (= I must be there at 10 o’clock.)