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Prepositions after adjectives

external + preposition

External is most commonly followed by to when something is outside a system, organisation, or body. Other prepositions usually have different meanings or are not standard complements.

Quick answer

Which preposition goes with external?

The standard pattern is external to when describing something outside a group, process, or structure. External as is possible when as introduces a role. External in, external of, and external for are usually not normal adjective complements, though the prepositions may appear in other parts of a sentence.

The auditor was external to the company.
These pressures are external to the education system.
She worked as an external consultant.

Choose the pattern by meaning

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

1
external to + organisation/system

Showing that something is outside a structure

Use external to for something that does not belong to or operate within a system, institution, or body.

The review panel is external to the university.
Several risks are external to our control.
2
external as + role

Describing a function or position

As can follow external when it introduces a role or identity, not as a fixed complement of the adjective.

He was hired as an external adviser.
The agency acted as an external partner.
3
external in + area

Referring to location or appearance

In may appear after external when it introduces a separate phrase about place or aspect.

The damage was mainly external in appearance.
The pipes are protected in external areas.

See the difference in context

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

Construction
Example
Meaning
external to
The software is external to the main network.
Standard pattern meaning outside or independent from something.
external as
She served as an external reviewer.
As introduces a role; it is not the normal complement of external.
external in
The crack is external in appearance only.
In usually introduces a separate detail such as area or aspect.
external of
The phrase external of the system is unusual in modern English.
External of is generally nonstandard as an adjective complement.
external for
External for the company sounds unnatural in most contexts.
For is not normally used directly after external.

Common mistakes

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

Using external of

Modern English normally uses external to, not external of.

✕ The consultant is external of the organisation. ✓ The consultant is external to the organisation.

Using external for as a complement

For usually does not follow external directly to show separation.

✕ The risk is external for the project. ✓ The risk is external to the project.

Confusing external as with external to

As introduces a role, while to shows separation from a system or group.

✕ She is external as the committee. ✓ She is external to the committee.

Quick practice

Choose the expression that matches the intended meaning.

1. The investigation was external ___ the department.
2. He worked as ___ external consultant.
3. Which phrase is most natural?

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Frequently asked questions

Is external to formal English?

Yes. It is common in academic, technical, legal, and business English.

Can I say external for?

Usually no. English normally uses external to when meaning outside a system or organisation.

What is the difference between external and outside?

Both can mean not inside something, but external is often more formal or technical.

eager-for-to-in-about, on "early in", "early on" or "early for"? earnest in, with, on, for or at? easy for, on, in, to or with? "economical with" or "economical in"? "ecstatic about" or "ecstatic with"? "effective in", "effective at" or "effective for"? "efficient in" or "efficient at"? elderly in, with, at, of or as? elegant in, with, of, as or to? eligible for, to, in or under? "embarrassed by" or "embarrassed about"?

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