zhèxiē dōngxi dōu xiánzhì le.

这些 means these and refers to more than one item, or to a group of items.

• 这东西 = this thing / this stuff
• 这些东西 = these things / this stuff here

So in this sentence, 这些 tells you the speaker is talking about a set of things, not just one.

Because 些 already does that job here.

In Mandarin, when you use 这 / 那 with a regular noun, you often need a measure word:

• 这本书 = this book
• 那个人 = that person

But with 些, you do not add another measure word:

• 这些书 = these books
• 那些人 = those people

So 这些东西 is completely normal. You would not say 这些个东西 in standard neutral usage unless you want a more colloquial or emphatic tone.

By itself, 东西 can mean thing, things, or stuff, depending on context.

Here, because it is preceded by 这些, it clearly refers to multiple items, so it is understood as these things or this stuff.

This is common in Chinese: the noun itself often does not change form for singular vs. plural. Context tells you.

When 东西 means thing / stuff, the second syllable is usually a neutral tone:

• 东西 = dōngxi

But when the two characters keep their literal meanings east and west, they are pronounced with their full tones:

• 东西 = dōng xī = east and west

So in this sentence, it is the common noun 东西 meaning things/stuff, so xi is neutral.

都 means all.

In this sentence, it says that all of these things are in the state of being 闲置.

Structure:

• 这些东西 = these things
• 都 = all
• 闲置了 = have been left idle / are now idle

So the sense is: These things are all sitting unused.

In Mandarin, 都 usually comes after the subject or topic it refers to and before the predicate.

So:

• 这些东西都闲置了

is the normal pattern:
these things + all + are idle / have been left idle

If you move 都 to the wrong place, the sentence may become unnatural or change meaning.

A useful pattern to remember is:

• A 都 + predicate
• 他们都来了 = They all came
• 这些东西都坏了 = These things are all broken
• 这些东西都闲置了 = These things are all idle / unused

It is mainly a verb, meaning to leave unused, to set aside, or to leave idle. But in actual sentences, it can also describe a resulting state, which makes it feel adjective-like in English.

That is why this sentence can be translated in more than one natural way:

• These things have been left idle
• These things are all unused now
• These things are all sitting idle

So grammatically in Chinese, 闲置 is verbal, but semantically it often describes a state.

Because Mandarin does not use 是 the way English uses to be in every sentence.

是 is mainly used to link one noun to another noun:

• 他是老师 = He is a teacher

But with adjectives, stative verbs, and many verbal predicates, you usually do not use 是:

• 他很忙 = He is busy
• 东西坏了 = The thing is broken
• 这些东西都闲置了 = These things are all idle / have been left unused

So 闲置 can directly serve as the predicate here. Adding 是 would usually sound unnatural in this sentence.

The 了 here marks a change of state or a new situation.

It does not simply mean past tense.

So 闲置了 suggests something like:

• they have become idle
• they ended up being left unused
• they are now idle

This often implies a contrast with an earlier situation, such as:

• they used to be used
• they were bought for a purpose
• now they are just sitting there unused

Without 了, the sentence would sound more like a general description:

• 这些东西都闲置 — not very natural by itself in conversation
• 这些东西都处于闲置状态 — these things are all in an idle state

So 了 makes the sentence more natural and dynamic.

In English, you might naturally say These things have been left idle, which sounds passive.

In Chinese, however, you often do not need 被 if the focus is on the result or state rather than on who did it.

So:

• 这些东西都闲置了

is already natural and can imply have been left unused.

If you want to make the passive meaning more explicit, you could say:

• 这些东西都被闲置了

That version is also grammatical, but it sounds a bit heavier and more explicitly passive. The original sentence is smoother and more natural when the agent is unimportant.

Yes, but the nuance changes.

• 这些东西闲置了 = These things have been left idle / are idle now
• 这些东西都闲置了 = These things are all idle

So 都 emphasizes that the statement applies to the whole set, not just some of it.

If there is already a plural group like 这些东西, adding 都 is very common when you want to stress every one of them.

Sometimes, but it would not feel quite the same.

• 这些东西都闲置了 = These things have ended up idle / are now idle
• 这些东西都闲置着 = These things are sitting idle
• 这些东西都闲置 = less natural in everyday speech as a standalone sentence

So 了 gives the sentence a strong state-change feeling. It is often the most natural choice when commenting on a current situation that has developed.

Yes, 闲置 is somewhat more formal or written than very casual spoken alternatives.

You often see it in:

• business contexts
• reports
• real estate
• inventory management
• discussions of equipment, property, or resources

For example:

• 闲置土地 = idle land
• 闲置资产 = idle assets
• 设备闲置了 = the equipment has been left unused

In casual speech, people might also say things like:

• 放着不用
• 一直没用
• 搁着没用

These are more conversational, while 闲置 sounds a bit more polished or formal.

The sentence follows a very common Mandarin pattern:

subject/topic + 都 + predicate + 了

So here:

• 这些东西 = subject/topic
• 都 = all
• 闲置 = predicate
• 了 = change-of-state marker

You can think of it as:

As for these things, they have all become idle / all been left unused.

This is a very useful pattern to recognize in many other sentences too.