What’s the difference?

English distinguishes auxiliaries and modal verbs. Auxiliaries (to be, to have, to do) combine with present participle or past participles or infinitive to form the verb forms of ordinary verbs. Modal verbs combine with infinitives to express ability, probability, necessity, permission, obligation, deduction etc.

auxiliariesmodal verbs
am-is-are 
was-werecan, could, to be able to
has-have-hadwill, won’t, shall, shan’t
to have towill,would, shall, should

When to use them

If you would like to practise the use of auxiliaries and/or modal verbs, please visit the pages modal mix and modalities.

modal mix: (can, could, may, might, must, had to, ought, shall, should, will, would)modalities: ability, permission, probability, deduction, necessity, request and obligation

The form of auxiliaries

Practise the form of the auxiliaries plus known problem areas such as the short yes/no answer and the tag-questions on the pages below.

am-is-are
was-were
has-have-had
to have to
short yes/no answer
tag-questions