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Preposition after adjective

Constant in, for, at, over or throughout?

Constant in is the main adjective pattern. Other prepositions usually introduce time spans, places, or ranges.

Quick answer

How is constant used with prepositions?

Use constant in for steady behaviour or qualities. For, at, over, and throughout usually add time or place information rather than forming fixed combinations.

She is constant in her support.
Prices stayed constant throughout the year.

Choose the pattern by meaning

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

1
constant in + quality/activity

Describing steady behaviour

Use constant in for regularity in actions or character.

He remained constant in his efforts.
2
constant for + period

Adding duration

For usually introduces a time period after constant.

The temperature stayed constant for two hours.
3
constant over + time

Showing no change during a period

Over introduces a span of time.

Demand remained constant over the summer.
4
constant throughout + area/period

Showing stability everywhere or all the time

Throughout refers to an entire period or place.

The tone was constant throughout the meeting.

See the difference in context

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

Construction
Example
Meaning
constant in
She is constant in her loyalty.
steady in behaviour or attitude
constant for
Output stayed constant for weeks.
for introduces duration
constant at
The speed remained constant at 60 km/h.
at introduces a level or value
constant over
Costs were constant over the decade.
stable during a period
constant throughout
Rainfall was constant throughout the night.
continuous during the whole period

Common mistakes

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

Confusing in with time expressions

Use in for behaviour, not duration.

✕ The pressure stayed constant in three days. ✓ The pressure stayed constant for three days.

Using at for personal qualities

At usually gives a value or point.

✕ She is constant at her beliefs. ✓ She is constant in her beliefs.

Quick practice

Choose the expression that matches the intended meaning.

1. He is constant ___ his support for the team.
2. The rate remained constant ___ several months.
3. Temperatures stayed constant ___ the winter.

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Frequently asked questions

Is constant in formal?

It is somewhat formal but still common in careful writing.

Can I say constant over time?

Yes. This is a common way to describe stability during a period.

What is the difference between constant and consistent?

Constant often means unchanging or continuous, while consistent often means regular or in agreement.

calm, in, calm, for, calm, about "candid about" or "candid in"? capable of or in? careful about, with, of, in or on? careless about, with, in, of or on? caribbean in, for, with, to or on? "catastrophic for" or "catastrophic to"? "cautious about" or "cautious in"? celtic in, for, on, at or to? central to, in, for, at or of? "certain of" or "certain about"? "challenging for" or "challenging of"?

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