lock up

2 meanings

Meanings
  1. 1 make a building safe by locking all the doors and windows B1
  2. 2 put someone in prison B2
1 lock sth up

make a building safe by locking all the doors and windows

B1

What does "lock up" mean in this sense?

To lock up means to make sure a building is fully secure before leaving — closing and locking all the doors and windows so that no one can get in. It is often used at the end of the working day, at night, or whenever the last person leaves a place. One of the most useful things about this phrasal verb is that you often don't need to name the building — if it's clear from the context, you can simply say 'lock up' and everyone understands. It's a very everyday expression, used equally in homes, offices, shops, and other workplaces.

Examples

How to use it

lock up (no object)

The most natural form in everyday speech — used when the building is already clear from the context.

Can you lock up when you leave? I have to go early.

lock up + place

Used when you want to name the building being secured.

She locked up the shop at half past five and walked to the bus stop.

lock + place + up

The noun object can also go between the verb and the particle — both word orders are natural.

He locked the office up and went home for the weekend.

lock + it/them + up

When using a pronoun instead of a noun, the pronoun must go between the verb and the particle.

The keys are on the table — use them to lock it up before you go.

be locked up

The passive form is used to describe the state of a building or to focus on whether it has been secured.

Please make sure the building is locked up before the cleaners arrive.

Common Collocations

lock up the houselock up the shoplock up the officelock up for the nightforget to lock upmake sure it's locked up

Common Mistakes

Always adding an object when none is needed

Learners often feel they must name the building every time, but native speakers very frequently use 'lock up' without any object when the place is obvious from context. Over-specifying can sound unnatural.

✗ Don't forget to lock up the building the office before you leave.
✓ Don't forget to lock up before you leave.
Wrong pronoun position

When you use a pronoun like 'it' instead of naming the place, the pronoun must go between 'lock' and 'up', not after 'up'.

✗ Can you lock up it tonight?
✓ Can you lock it up tonight?
Confusing 'lock up' with 'lock out'

'Lock up' means to secure a building when leaving. 'Lock out' means to accidentally or deliberately stop someone from getting in. They describe very different situations.

✗ I forgot my keys and locked up myself.
✓ I forgot my keys and locked myself out.

Usage

This phrasal verb is neutral and works in both spoken and written English. It is equally common in British and American English, and very frequently appears in the imperative or with modal verbs like 'don't forget to' or 'remember to'.

2 lock sb up

put someone in prison

B2

Sense 2: What does "lock sb up" mean?

To lock someone up means to put them in prison as punishment or while awaiting trial. It is used when a court, judge, police force, or government officially incarcerates a person following a crime or legal process. The phrase is neutral to informal in tone and is extremely common in everyday conversation, news reporting, and journalism. It is also used hyperbolically to express strong disapproval — someone might say 'that driver should be locked up!' without literally meaning a prison sentence. In formal legal contexts, writers tend to prefer 'imprison' or 'incarcerate', but 'lock up' is perfectly natural in most other situations.

Examples

How to use it

be locked up (for + crime/time)

The passive is the most frequent pattern for this sense and sounds completely natural without needing to mention who did the imprisoning.

She was locked up for three years after the fraud case was finally resolved.

lock + pronoun + up

When the object is a pronoun, it must always go between 'lock' and 'up' — it cannot follow the particle.

The evidence was overwhelming, so the police locked him up immediately after the hearing.

lock + short noun object + up

Short noun phrases can also be placed between 'lock' and 'up', especially when referring to a specific individual.

The court decided to lock the suspect up pending further investigation.

lock up + longer noun phrase

When the object is a longer or more complex noun phrase, it typically follows the particle without separation.

The government promised to lock up anyone found guilty of large-scale corruption.

should/deserve to be locked up

This construction is very common for expressing strong disapproval or a judgement that someone ought to be imprisoned.

Anyone who runs a scam like that deserves to be locked up.

Common Collocations

locked up for fraud/murder/theftlocked up for years/lifeshould be locked upend up locked upwrongly locked uplock up criminals/suspects

Common Mistakes

Pronoun placement

When the object is a pronoun such as 'him', 'her', or 'them', it must always come between 'lock' and 'up'. Placing the pronoun after 'up' is incorrect in English.

✗ The judge decided to lock up them for life.
✓ The judge decided to lock them up for life.
Confusing the two senses of 'lock up'

In this sense, the object must always be a person — never a place or object. If you use a building, shop, or room as the object, it shifts to a completely different meaning (securing a building). Always check that your object refers to a person.

✗ The warden locked up the prison at night. (if you mean 'imprisoned someone')
✓ The warden locked up the offender before lights out.
Confusing 'lock up' with 'lock away'

'Lock away' and 'lock up' both mean to imprison, but 'lock away' also applies to storing objects securely ('lock away your valuables'). If you use 'lock up' with an object, make sure it refers to a person so the meaning stays clearly in the prison sense.

✗ I'll lock up my passport in the safe. (This could cause confusion — 'lock away' is more natural here.)
✓ I'll lock away my passport in the safe.

Usage

This phrasal verb is neutral to informal and suits everyday speech, news, and journalism; in formal legal writing, prefer 'imprison' or 'incarcerate'. The passive form 'was locked up' is by far the most common pattern and sounds very natural.

Frequently Asked Questions

Does 'lock up' always mean securing a building? It sounds like it could mean something else.

No, it doesn't always refer to buildings. 'Lock up' can also mean to put someone in prison — for example, 'The judge decided to lock him up.' The key difference is the object: if the object is a person, it usually means imprisonment; if the object is a place (or there's no object), it means securing a building.

Can I say 'I am locking up the house right now'?

Yes, this is grammatically fine if you are actually in the middle of doing it at that exact moment. However, the present continuous is not very common with 'lock up' in this sense — it sounds more natural in the simple past, present perfect, or with a modal verb, like 'I've locked up' or 'I need to lock up'.

Is 'lock up for the night' a fixed phrase?

It's not completely fixed, but it is a very common and natural combination. You'll often hear it in workplaces and homes when the last person is leaving at the end of the day — for example, 'Who's going to lock up for the night?' It has a routine, end-of-day feeling to it.

What kinds of places can you 'lock up'?

Any enclosed space that can be secured with a lock — houses, flats, shops, offices, schools, warehouses, and so on. The most common collocations are 'lock up the house', 'lock up the shop', and 'lock up the office'. You wouldn't normally use it for something like a car or a safe — there are more specific verbs for those.

Is 'locked up' used more than 'lock up' in sentences?

Yes — the passive form 'was/were locked up' is actually the most common way this phrasal verb appears in real English. Sentences like 'He was locked up for five years' sound very natural and are found constantly in news articles and everyday speech. Active forms like 'they locked him up' are also correct but less frequent.

Can 'lock up' be used in a joking or exaggerated way, not about real prison?

Absolutely. Saying something like 'That referee should be locked up!' is a very natural hyperbolic expression of frustration or disapproval. In these cases, the speaker does not literally mean imprisonment — it is just a strong way of saying someone's behaviour is unacceptable. This kind of usage is common in informal conversation.

Can I say 'they are locking him up right now'?

It is possible but quite rare. The present continuous sounds a little awkward for this phrasal verb unless you are describing something happening at that exact moment. In most situations, a simple past or passive construction ('he was locked up', 'they locked him up') will sound more natural.

Does 'lock up' only apply to prison, or can it mean being sent to a psychiatric facility?

In standard usage, 'lock up' in this sense refers to prison or criminal detention. If someone is being committed to a psychiatric institution, the more typical phrasal verb would be 'put away'. Keeping 'lock up' linked to criminal or legal contexts will help you avoid any ambiguity.

What kinds of crimes or time periods commonly follow 'locked up'?

The pattern 'locked up for + crime' or 'locked up for + time' is extremely productive. Common examples include 'locked up for fraud', 'locked up for theft', 'locked up for murder', 'locked up for ten years', and 'locked up for life'. You can also say 'locked up without trial' when no legal process has taken place.

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