Base Form
Learn where the base form of a verb is used, how it appears in the present simple, and why it never takes an ending after a modal verb.
The plain form
The base form is a verb with nothing added to it.
The base form is a verb’s plain, uninflected form. It carries no tense, no ending, and no marker of who is performing the action, and it serves as the foundation every other verb form is built from.
In She can work from home., work is the base form. It follows the modal verb can directly, with no -s, -ing, or -ed added to it.
This lesson covers where the base form appears, including its role in the present simple tense.
Before you begin
The base form is one of five topics on verb forms.
This lesson focuses on the base form specifically. Verb forms as a whole include four other topics, each covered in its own lesson.
If you would like an overview of verb forms in general, begin with the Verb Forms page.
The central idea
Every other form starts from the base form.
Compare the base form with a form that has something added to it.
01
Base form
work
02
With something added
works, working, worked
The useful question is: what, if anything, has been added to this word?
Work has nothing added. Every other form of this verb, whatever ending or change it takes, starts from this same base.
Where the base form is used
Several structures call for the base form specifically.
After a modal verb
She must finish the report.
Modal verbs such as can, will, must and should are always followed by the base form.
In the infinitive, after to
She wants to finish the report.
In a command
Finish the report by five.
With do, does or did
She doesn’t finish early. / Did she finish early?
Once do, does or did carries the tense, the main verb returns to its base form.
The base form in the present simple
Most subjects use the plain base form.
I, you, we and they use the base form directly
I work. They work.
He, she and it add an -s
She works.
This is the one place a base form does not stay fully unchanged when it stands as the main verb of a sentence.
A useful decision guide
Ask what comes directly before the verb.
01
Does a modal verb come before it?
If so, the base form is needed, with no ending added.
02
Does to come before it, as part of an infinitive?
The base form follows directly.
03
Does do, does or did appear elsewhere in the sentence?
The main verb returns to its base form once one of these is present.
04
Is the subject he, she or it, with no other auxiliary verb?
An -s is added to the base form in the present simple.
Common mistakes
Modal verbs and do support both call for the plain base form.
An -s is not added after a modal verb.
Not: She can works from home.
Correct: She can work from home.
To is not added after a modal verb.
Not: She can to work from home.
Correct: She can work from home.
Unlike many other verbs, modal verbs are followed directly by the base form, without to in between.
The main verb keeps its base form after do, does or did.
Not: Does she works from home?
Correct: Does she work from home?
Check your understanding
Which form correctly completes each sentence?
Choose the correct answer for each sentence.
They should __________ before the storm arrives.
✅ Exactly! The modal verb “should” is followed by the base form.
❎ Not quite. Check what kind of word comes right before this verb.
Is “should” a modal verb?
Does the train usually __________ on time?
✅ Exactly! “Does” already carries the present tense, so the main verb returns to its base form.
❎ Not quite. “Does” is already present in this question.
Is “does” already carrying the tense here?
He __________ dinner every evening.
✅ Exactly! With “he” as the subject in the present simple, an -s is added.
❎ Not quite. There is no auxiliary verb here, and the subject is “he”.
Is there a modal verb, or an auxiliary verb, here at all?
Choose the best explanation
Select the sentence that explains the mistake correctly.
Why is “She can to work from home.” not correctly formed?
✅ Exactly! “To” is not used between a modal verb and the base form.
❎ Not quite. Focus on the word “to” and what follows the modal verb “can”.
Why is “Does she works from home?” not correctly formed?
✅ Exactly! Once “does” is present, the main verb does not take its own -s ending.
❎ Not quite. Look at the ending on “works” here.
Quick review
The base form appears wherever the tense is already carried by another word.
The base form is a verb’s plain form, with no ending added.
It follows modal verbs, appears after to in the infinitive, forms commands, and follows do, does or did.
In the present simple, most subjects use the base form directly; only he, she and it add an -s.
Remember
Check what already carries the tense before adding anything to the verb.
If a modal verb, to, or a form of do is already present, the verb itself stays in its plain, unchanged base form.