Пятновыводитель нужен.

Because it is the thing being described as needed. In this sentence, пятновыводитель is the grammatical subject, so it appears in the nominative singular.

• пятновыводитель = stain remover
• nominative singular masculine noun

So the structure is basically:

• Пятновыводитель = the stain remover
• нужен = is needed / is necessary

Because нужен agrees with пятновыводитель, which is a masculine singular noun.

Agreement works like this:

• нужен — masculine singular
• нужна — feminine singular
• нужно — neuter singular
• нужны — plural

Since пятновыводитель is masculine singular, Russian uses нужен.

For comparison:

• Соль нужна. = Salt is needed.
• Мыло нужно. = Soap is needed.
• Перчатки нужны. = Gloves are needed.

Нужен is the short form of the adjective нужный.

• full form: нужный = necessary, needed
• short form: нужен = needed / necessary

In Russian, short-form adjectives are often used in sentences like this, especially when stating a condition or necessity.

So:

• нужный пятновыводитель = a needed/necessary stain remover
• Пятновыводитель нужен. = The stain remover is needed. / Stain remover is needed.

The short form sounds natural here. The full form would not usually be used in this exact sentence.

In the present tense, Russian normally does not use a separate word for is/am/are.

So English:

• The stain remover is needed

becomes Russian:

• Пятновыводитель нужен.

This is completely normal. Russian often leaves out the present-tense to be.

Compare:

• Он дома. = He is at home.
• Кофе горячий. = The coffee is hot.
• Пятновыводитель нужен. = Stain remover is needed.

It can often be understood in a broader English way as We need stain remover, depending on context.

Literally, the Russian structure is closer to:

• Stain remover is needed

But in real usage, that often implies:

• We need stain remover
• A stain remover is necessary
• Stain remover is required

Russian does not always state who needs it if that is obvious from context.

Yes. Russian word order is flexible.

You can say:

• Пятновыводитель нужен.
• Нужен пятновыводитель.

Both are correct, but the emphasis changes slightly.

A rough way to feel the difference:

• Пятновыводитель нужен. — talking about the stain remover, saying that it is needed
• Нужен пятновыводитель. — emphasizing that what is needed is a stain remover

The second version can sound a bit like What we need is stain remover.

Yes. Russian often forms long compound words, and пятновыводитель is one of them.

It is built from parts related to:

• пятно = stain
• выводить / вывести = to remove, to get out
• -тель = a suffix often used for a tool or agent

So пятновыводитель literally means something like stain-remover.

This kind of compound is very normal in Russian.

They are similar, but not exactly the same.

• Пятновыводитель нужен. = Stain remover is needed.
• Надо пятновыводитель. = not standard Russian

If you use надо, the structure changes:

• Нужен пятновыводитель.
• Надо купить пятновыводитель. = It is necessary to buy stain remover.
• Нам нужен пятновыводитель. = We need stain remover.

So нужен agrees with a noun, while надо is more impersonal and usually goes with an infinitive or a whole idea.

Yes. You can say:

• Нам нужен пятновыводитель. = We need stain remover.

Here нам means to us, and it often corresponds to English we need.

This is very common in Russian:

• Мне нужен врач. = I need a doctor.
• Тебе нужна помощь. = You need help.
• Нам нужен пятновыводитель. = We need stain remover.

Without нам, the sentence is a bit more general or context-dependent.

A helpful approximate pronunciation is:

pyat-na-vy-VA-di-tyel’

A few notes:

• я after п gives something like pya
• the stress is on во
• the final -тель sounds roughly like tyel’
• the soft sign ь does not have its own sound, but it softens the preceding consonant

If you want a rougher English-style guide, you can think of it as:

pyat-nuh-vih-VOH-dih-tyel

Not perfect, but useful as a start.

Yes, it sounds natural, especially in context.

For example, if people are cleaning and someone notices a stain, they might say:

• Пятновыводитель нужен.

It is short, natural, and idiomatic. Russian often uses brief sentences like this when the situation is already clear.

If you wanted to sound a little fuller or more explicit, you could also say:

• Нам нужен пятновыводитель.
• Нужен пятновыводитель для этого пятна. = We need a stain remover for this stain.