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Prepositions after verbs

Reinforce by, with, in, at, or for?

Reinforce with is the most common pattern for adding support or material. Reinforce by is also used for methods.

Quick answer

Which prepositions work with reinforce?

Use reinforce with for added support, material, or help. Use reinforce by for the method used to strengthen something. Reinforce in, at, and for are not standard fixed combinations after reinforce.

The wall was reinforced with steel beams.
The lesson was reinforced by practical exercises.
They reinforced with extra staff.

Choose the pattern by meaning

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

1
reinforce with + support/material

Adding strength or support

With introduces the thing added to make something stronger.

The bridge was reinforced with concrete.
Security was reinforced with additional guards.
2
reinforce by + method

Showing how reinforcement happens

By introduces the action or method that strengthens something.

The message was reinforced by repeated reminders.
3
reinforce against + threat

Protecting from danger

Against is often used when strengthening protection from damage or attack.

The windows were reinforced against storms.
4
reinforce in + place

Using in as a place adjunct

In usually describes location rather than forming a fixed pattern with reinforce.

Troops were reinforced in the northern region.

See the difference in context

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

Construction
Example
Meaning
reinforce with
The roof was reinforced with metal bars.
Shows the added support or material.
reinforce by
Confidence is reinforced by success.
Shows the method or cause of strengthening.
reinforce in
The army was reinforced in the capital.
In refers to place, not a fixed verb-preposition pattern.
reinforce at
They reinforced security at the airport.
At introduces location.
reinforce for
The team trained for the final.
For is not normally selected by reinforce itself.

Common mistakes

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

Using reinforce for as a fixed pattern

For usually belongs to another part of the sentence, not directly to reinforce.

✕ The structure was reinforced for steel cables. ✓ The structure was reinforced with steel cables.

Confusing with and by

With names what is added; by names the method or cause.

✕ The wall was reinforced by concrete. ✓ The wall was reinforced with concrete.

Using at as the support element

At normally marks location, not the reinforcing material.

✕ The gate was reinforced at metal panels. ✓ The gate was reinforced with metal panels.

Quick practice

Choose the expression that matches the intended meaning.

1. The fence was reinforced ___ wooden posts.
2. Her argument was reinforced ___ recent data.
3. Police presence was reinforced ___ the stadium.

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Frequently asked questions

What is the difference between reinforce with and reinforce by?

With names the added support, while by explains the method or cause.

Is reinforce in correct?

Only when in introduces a place or context, such as reinforced in the city.

Can reinforce be used without a preposition?

Yes. For example: They reinforced the bridge.

radiate-from-into-around-to, with "raise in" or "raise by"? rake in, through, across, at or over? rally in, around, to, behind or on? "rape by" or "rape in"? ratify by, in, on, according or as? ravage by, from, on, through or with? rave about, at, from, to or before? reach for, by, at, to or into? react to, with, in, by or like? read about, in, on, through or for? "realize in", "realize at" or "realize by"?

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