Prepositions with necessity

Of necessity or by necessity?

Both expressions exist, but they are used differently. Of necessity is a formal fixed phrase meaning inevitably, while by necessity is uncommon and usually replaced by out of necessity or by necessity of circumstance.

Quick answer

Which form is correct?

Of necessity is a formal idiomatic phrase meaning “necessarily” or “inevitably.” By necessity is not a standard fixed expression in modern English. In most contexts, use out of necessity or by necessity of circumstance instead.

The project was delayed of necessity because funding arrived late.
She took the extra job out of necessity after the move.
The changes were made of necessity rather than preference.

Choose the pattern by meaning

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

of necessity

Expressing inevitability or necessity

This formal phrase means that something must happen because circumstances require it.

The meeting was short of necessity.

Their response was cautious of necessity.

out of necessity

Explaining the reason for an action

Use this common phrase when someone does something because they have no better option.

He learned to cook out of necessity while living abroad.

Many families reduced spending out of necessity.

necessity for + noun

Showing what is needed

Use necessity for before a noun that is required or important.

There is a clear necessity for change.

Doctors stressed the necessity for rest after surgery.

See the difference in context

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

Construction

Example

Meaning

of necessity

The decision was, of necessity, temporary.

A formal phrase meaning inevitably or necessarily.

by necessity

They acted by necessity of circumstance.

Possible in limited formal wording, but uncommon on its own.

out of necessity

She moved back home out of necessity.

The usual modern expression for acting because of need.

necessity for

We discussed the necessity for stricter rules.

Shows what is needed.

Common mistakes

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

Using by necessity as a general fixed phrase

By necessity alone sounds unnatural in most modern contexts.

✕ He worked nights by necessity. ✓ He worked nights out of necessity.

Confusing of necessity with possession

Of necessity is an idiomatic adverbial phrase, not a possessive structure.

✓ The process was slow of necessity.

Using necessity without an article where one is needed

Countable uses often need a or the.

✕ It became necessity. ✓ It became a necessity.

Quick practice

Choose the expression that matches the intended meaning.

1. The repairs were delayed ___ because the parts had not arrived.

2. She accepted the temporary job ___ after losing her apartment.

3. There is a growing ___ stricter safety checks.

Check your sentence in context

Paste the complete sentence below. Linguix checks the preposition together with grammar, spelling, punctuation, and style.

Free to try · No signup required

Frequently asked questions

Is by necessity wrong?

It is not completely wrong, but it is uncommon without extra wording such as by necessity of circumstance.

Is of necessity formal?

Yes. It is mainly used in formal or literary English.

What is the most natural everyday expression?

Out of necessity is the most common choice in everyday English.

Write with confidence in Linguix

Create a free account to check complete texts, apply suggestions, and save your documents.

Create a free account