by Sentenceworks
Modal Verbs
Modal verbs are verbs which modify another verb, and imply the possibility or probability of something happening. Modal verbs are words like “can”, "will", "could", "must", "would", “might” and “should”.Modal Verb + To + Infinitive
After a modal verb, the root form of the word is generally used. We do not use the infinitive after a modal verb.
Incorrect: We would to study more of Shakespeare’s works if we had the books.
The modal verb, “would”, does not need to be followed by the infinitive. “To” should be removed from this sentence.
Exception:
The phrase, “ought to” is considered a modal verb. In this case, the “to” belongs with the “ought”, and is not considered part of the infinitive.
Correct: Pet owners ought to vaccinate all their outdoor pets.
Incorrect: Pet owners ought not let their unvaccinated pets out of doors.
The modal verb phrase, “ought to” is missing “to”. “To” should be inserted after “not”.
Modal verb + another modal verb
If two modal verbs are used in the same clause, it may make it difficult for the reader to understand. It is acceptable to use two modal verbs in the same sentence, providing they are in separate clauses.
Incorrect: Should he must finish the report by tomorrow?
Both “should” and “must” are modal verbs, and should not be used in the same clause. The sentence could be written as, “Should he finish…” or “Must he finish…”.
Don’t forget to check for modals in the future tense:
Incorrect: Shall I will finish the project tomorrow?
“Shall” and “will” are both modal verbs. “Will” or “shall” should be removed from the sentence, depending on the intended meaning.
Correct: Must he finish the report tonight, or should he finish it tomorrow morning?
Because “must” and “should” are in separate clauses, this sentence is considered to be correct.
After A Modal Verb
After a modal verb, the verb which is being modified should be in its root form.
Incorrect: He must does many years of practical work before he can be considered an expert.
“Does” should be changed to its root form, “do”, because it is being modified by a modal verb.
Incorrect: Mary and Mark may flew to Newfoundland instead of drive.
“Flew” should be changed to its root form, “fly”, because it is being modified by a modal verb.
Inflected Endings
Modal verbs are always written in the root form, and do not require special endings to identify tense or person.
Incorrect: The president oughted to have approved larger holiday bonuses last year.
Despite the sentence being in past tense, the modal verb does not require the ending, “ed”. The sentence should be written: The president ought to have approved….
Incorrect: Cathy shoulds think about other people when she smokes in the washroom.
Modal verbs do not need a special ending for third-person. The “s” should be removed from the end of “shoulds”.
Negatives and Questions With "Do" Auxiliaries
When writing a question, or a negative statement, the verb, “do”, is generally not used with a modal verb.
Incorrect: He didn’t could understand what I was trying to say.
The modal verb, “could”, makes the verb, “didn’t”, unnecessary. The negative can be applied to the modal verb: He couldn’t understand what I was trying to say.
Incorrect: Do you can understand what I’m trying to say?
The modal verb, “can”, makes the verb, “do”, unnecessary. One of these verbs should be removed: Do you understand… or Can you understand….
Root Form, Not Perfect Tense
When using a perfect tense (in past, present or future) after a modal, ensure the perfect tense verb is in the root form.
Incorrect: By tomorrow, he might will have finished the work.
Despite this sentence being in the future tense, the future perfect verb should be in its root form because it follows a modal verb: By tomorrow, he might have finished….
Incorrect: Kate could had finished eating her meal, but she was anxious to leave the house.
Despite this sentence being in the past tense, the past perfect verb should be in its root form because it follows a modal verb: Kate could have finished eating her meal….