1. What exactly can't negates
When talking about ability, can means “know how to / be able to,” while can't means “not know how to / not be able to.” It refers to the ability to perform a specific action, not to a person's worth or desire.
A sentence without additional words does not promise that things will always be this way. A person may learn, or circumstances may change.
I can't skate.
I don't know how to skate.
In a discussion of skills, this negates the ability to skate.
We cannot read this map.
We cannot read this map.
The limitation concerns this specific map; the reason depends on the situation.
2. One construction for all persons
After can't / cannot, use the base form of the verb without to: read, help, use. Do not add -s even after he, she, or the name of one person.
Can't already contains the negation. This construction does not need don't, doesn't, am, is, or are.
Subject + can't / cannot + verb without to + the rest of the sentence
- subject / S —
- The grammatical subject: who or what the clause is about; the verb agrees with it. In The book was written, the book is the subject, although someone else does the action.
- verb / V —
- A word for an action or state, such as work or be. The pattern determines its form.
Marta can't fix the radio.
Marta can't fix the radio.
After can't, use fix, not fixes: the number of people does not change the form.
They can't carry the table.
They can't carry the table.
Use the same construction after plural they.
3. Can't, cannot, and spelling
Can't is the usual contracted form; cannot is the usual full form written as one word. Both can express the same meaning. Can't is natural in conversation and informal writing; cannot is suitable both in writing and for emphasis in speech.
For an ordinary negative statement, choose can't or cannot. The spelling can not also occurs as an acceptable option: do not always consider it a grammatical error. Separate not can also belong to another expression, such as not only. This is not the main pattern of this lesson.
Can't requires an apostrophe. If an exercise specifically asks for the full or contracted form, that is a spelling-practice requirement, not a ban on the other form in English.
He can't open the jar.
He can't open the jar.
A natural option for ordinary conversation.
He cannot open the jar.
He cannot open the jar.
The same inability to open the jar, but in the full form.
4. Can't right now does not mean “never know how”
Can't is also suitable for a present obstacle: noise makes it difficult to hear, the text is too small, or the object is too heavy. Now, today, or an explanation of the reason helps define the situation.
Do not confuse inability with prohibition. In You can't park here, the reason may be that parking is not allowed. I can't come tonight may report that someone is busy, not that they lack the ability to come. Context determines the meaning.
Couldn't can grammatically describe past inability. Here we are practicing a present situation; talking about the past requires a separate choice of form.
I can't hear you. The music is loud.
I can't hear you. The music is loud.
The obstacle exists now; this is not a statement about a permanent inability to hear.
You can't park here. Parking is not allowed.
You can't park here. Parking is not allowed.
This is a grammatically correct prohibition, but it is a different meaning of can't.
I couldn't read this word yesterday.
I couldn't read this word yesterday.
The correct form for a past situation, not a replacement for can't when reporting about now.
5. Not very well, not at all, not yet
Can't … very well negates doing an action well, but not necessarily the ability altogether. A person may be able to cook simple dishes, but not very well.
At all strengthens the negation: “completely.” Yet in this type of sentence means “still”: the ability or result is not present so far. Choose the clarification according to the facts; do not add complete inability without a basis.
They can't cook very well.
They can't cook very well.
This does not mean that they are completely unable to prepare food.
I can't swim at all.
I can't swim at all.
At all directly strengthens the negation of the ability.
She can't ride a bike yet.
She can't ride a bike yet.
Yet shows that the skill is not present so far, without promising an exact time for learning.
6. Short answers and the next step
You can answer a question about ability with No, I can't. If you are talking about another person, choose the appropriate pronoun: No, she can't. It is not necessary to repeat the verb from the question.
In a real conversation, it is useful to clarify the action or suggest the next step: ask for help or say what you can do instead. Sorry can soften the reply, but an apology is not required.
Can + subject + verb …? → No, + subject + can't / cannot.
- subject / S —
- The grammatical subject: who or what the clause is about; the verb agrees with it. In The book was written, the book is the subject, although someone else does the action.
- verb / V —
- A word for an action or state, such as work or be. The pattern determines its form.
Can you play chess? — No, I can't.
Can you play chess? — No, I can't.
In the answer, the speaker changes from you in the question to I.
I can't move this desk alone. Can you help me?
I can't move this desk alone. Can you help me?
First, a specific inability is stated; then an appropriate request for help is made.
Common mistakes
Incorrect:She can't speaks English.
Correct:She can't speak English.
After can't, use the base form speak; do not add the -s ending here.
Incorrect:I can't to cook.
Correct:I can't cook.
After the modal can't, there is no to before the main verb.
Incorrect:He doesn't can read the sign.
Correct:He can't read the sign.
Form the negative of can with can't / cannot, not with doesn't can.
Incorrect:We can't using this tool.
Correct:We can't use this tool.
For the action after can't, use use, not the form using.