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Prepositions after adjectives

Proficient in or proficient at?

Both proficient in and proficient at are idiomatic. Use in for a field, language, or subject area, and at for a skill or activity.

Quick answer

Which preposition is correct with proficient?

Use proficient in for knowledge areas or subjects and proficient at for practical skills or activities. Both are standard English.

She is proficient in Spanish.
He became proficient at coding.

Choose the pattern by meaning

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

1
proficient in + subject

Knowledge or field of expertise

Use proficient in with languages, subjects, software, or professional areas.

They are proficient in data analysis.
2
proficient at + activity

Skill in performing an activity

Use proficient at with tasks, games, or practical actions.

She is proficient at negotiating contracts.

See the difference in context

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

Construction
Example
Meaning
proficient in
He is proficient in French.
Skilled in a subject, language, or field.
proficient at
She is proficient at repairing engines.
Skilled at performing an activity.
proficient with
The designer is proficient with Adobe Illustrator.
Sometimes used for tools or software.

Common mistakes

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

Using at with a subject area

Subjects and fields usually take in.

✕ She is proficient at mathematics. ✓ She is proficient in mathematics.

Using in with an action

Activities often sound more natural with at.

✕ He is proficient in cooking Italian meals. ✓ He is proficient at cooking Italian meals.

Quick practice

Choose the expression that matches the intended meaning.

1. She is proficient ___ accounting software.
2. He became proficient ___ public speaking.
3. They are proficient ___ several languages.

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Frequently asked questions

Can I say proficient at something?

Yes. Proficient at is standard for activities and practical skills.

Is proficient in more common than proficient at?

Proficient in is especially common with subjects, languages, and professional fields.

Can proficient be followed by with?

Sometimes. Proficient with is used for tools, equipment, or software.

packed-with-to-in-on, into "paid for" or "paid up"? painful for, to, in, at or of? "palatable to" or "palatable for"? "pale in" or "pale of"? "pandemic of" or "pandemic in"? "paramount to" or "paramount in"? paranoid about, of, in, with or over? partial to, of, in, towards or for? participating in, of, on, at or for? "particular about" or "particular to"? part-time at, in, for, as or with?

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