Modal verbs are used to talk about ability, to ask permission, to make requests, and to give advice. Modal verbs are placed after the subject and before the main verb. The main verb the follows them will be in the base form, with no -s even if the subject is 3rd person singular. Modals are used in academic writing for similar reasons as in other writing. They are also used in hedging expressions, to make conclusions more precise and careful.
He should goes to the dentist twice a year.
He should go to the dentist twice a year.
You can also use some modals to express degrees of certainty about conclusions. The strongest model of conclusion is must. Must is rarely used in academic writing, because conclusions should be more hesitant and less , and if things are known facts, or results of evidence presented to support these claims, they can be presented with no modal.
More frequently, may/might/could are used to express the possibility that something might be true, without committing to it being definitely true. Similarly, can’t, as an expression of certainty that something is not true, is rarely used, except when we have proven that conclusion based on evidence presented.
One difficulty with using modals has to do with how few modals there are in English, and how many purposes they are used for. All ten of them are listed below. See articles for specific modal types for more details:
- has/have to