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Preposition after adjective

Incompetent in or incompetent at?

Both incompetent at and incompetent in are used, but they describe different things. Use at for activities or skills and in for areas, jobs, or fields.

Quick answer

Which preposition goes with incompetent?

Use incompetent at for activities, tasks, or skills: incompetent at driving. Use incompetent in for a field, role, or area: incompetent in financial management.

He is incompetent at parking.
The manager was incompetent in handling staff complaints.
She felt incompetent at public speaking.

Choose the pattern by meaning

These forms are not interchangeable. Choose the construction by meaning, not by which preposition appears most often.

1
incompetent at + activity

Talking about poor ability in a skill or task

Use at with activities, games, practical tasks, and skills.

I'm incompetent at cooking rice.
He became incompetent at using the software.
2
incompetent in + field

Talking about poor performance in an area or role

Use in with professions, departments, subjects, or broad areas of responsibility.

The agency was incompetent in crisis management.
She is incompetent in administrative work.
3
incompetent to + verb

Talking about inability or lack of qualification

In formal contexts, incompetent to can mean not capable or not legally qualified to do something.

He was declared incompetent to stand trial.
The officer proved incompetent to lead the investigation.

See the difference in context

The same subject can take different constructions because each sentence answers a different question.

Construction
Example
Meaning
incompetent at
She is incompetent at budgeting.
Used for skills, tasks, and activities.
incompetent in
He was incompetent in his role as supervisor.
Used for areas of work, responsibility, or fields.
incompetent to
The patient was found incompetent to make legal decisions.
Formal use meaning not capable or not qualified to do something.

Common mistakes

Some combinations appear in real text but do not mean what learners often assume.

Using in for a specific skill

Use at for practical activities and skills.

✕ He is incompetent in chess. ✓ He is incompetent at chess.

Using at for a professional field

Use in for broad areas or roles.

✕ She was incompetent at human resources management. ✓ She was incompetent in human resources management.

Confusing incompetent to with at

Incompetent to usually appears in formal or legal contexts.

✕ He is incompetent to cooking. ✓ He is incompetent at cooking.

Quick practice

Choose the expression that matches the intended meaning.

1. She is incompetent ___ managing large teams.
2. The report described the department as incompetent ___ safety procedures.
3. The court ruled him incompetent ___ stand trial.

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Frequently asked questions

Is incompetent at more common than incompetent in?

They are both standard, but they are used in different contexts. At usually refers to skills and activities, while in refers to fields or roles.

Can I say incompetent in math?

Yes. Math can be treated as a field of study, so incompetent in math is natural.

Is incompetent to informal?

No. Incompetent to is mainly formal and often appears in legal or official language.

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