Last week, we explored modal verbs of certainty and uncertainty. Today we move on to obligation and permission. Obligation means that we have to do something. We don’t have a choice; it’s mandatory. Permission is about what we are allowed to do. Here we go:
Modal verbs such as must, will and need express a strong sense of obligation. For example,
You must take off your shoes at the door.
All students will be at their desks at 9am.
You need to be at the station at 3pm.
The opposite of obligation is prohibition, and we can use these verbs as well as may not and can not/cannot to express this:
You may not cross this line. This means the same as ‘You must not cross this line.’
If you don’t have a ticket, you cannot board the bus.
A weaker sense of obligation is expressed by the modal verbs should, ought to and might:
You should leave work earlier than this.
We ought to eat more vegetables.
You might ask the others if they would like a coffee. (This is a rather distanced and therefore more polite way of telling someone to do something.)
Finally, permission. The modal verbs may, can and could are used to express a sense of permission, to show what someone is permitted to do:
You may leave your bag here.
The children can play at lunchtime.
You could stop for a rest if you want.
Please note that these lists of modal verbs are not exhaustive, and there can be some overlap in meaning. There is no substitute for wide reading and practice, if you are able to do that. The more we experience these expressions in context, the more understanding we will gain about how to use and interpret them.
As always, my ‘go-to’ grammar text is Michael Swan’s Practical English Usage.
Next week, we will conclude our exploration of modal verbs with freedom and ability to act.
