Напёрсток нужен, чтобы штопать.

Нужен is the short form of the adjective нужный and it means is needed / is necessary.

It agrees with напёрсток, which is:

• masculine
• singular
• nominative

So:

• напёрсток нужен = the thimble is needed

Compare:

• нож нужен = the knife is needed
• книга нужна = the book is needed
• окно нужно = the window is needed
• деньги нужны = money is needed

The full form нужный usually means needed as a descriptive adjective, like a needed thing, not is needed in this sentence.

It is in the nominative case because it is the grammatical subject of the sentence.

Structure:

• Напёрсток = subject
• нужен = predicate
• чтобы штопать = purpose clause

So the basic idea is:

• A thimble is needed...
• ...in order to darn.

Here чтобы means in order to / so as to and introduces a purpose.

So:

• Напёрсток нужен, чтобы штопать. = A thimble is needed in order to darn.

A longer, more explicit version is:

• Напёрсток нужен для того, чтобы штопать.

That means the same thing, but для того is often omitted because чтобы alone is very common and natural.

It is in the infinitive because after чтобы Russian often uses the infinitive when the sentence expresses a general purpose, especially when no specific subject is stated.

So:

• чтобы штопать = to darn / in order to darn

This is similar to:

• Нож нужен, чтобы резать. = A knife is needed to cut.
• Ручка нужна, чтобы писать. = A pen is needed to write.

If you want to name the person doing the action, Russian often uses a finite verb instead:

• Мне нужен напёрсток, чтобы я могла штопать. = I need a thimble so that I can darn.

Russian often leaves the subject unstated when the meaning is general.

So чтобы штопать does not mean that a specific person is missing; it just means:

• for darning
• to darn
• in order to darn

English often uses you, one, or just the infinitive:

• You use a thimble to darn
• A thimble is needed to darn
• One needs a thimble to darn

Russian is happy to keep this impersonal and general.

No, not exactly.

• шить = to sew
• штопать = to darn / mend by stitching, especially holes in socks, clothes, fabric, etc.

So штопать is more specific. It is not general sewing; it is repairing fabric with stitches.

Examples:

• Она шьёт платье. = She is sewing a dress.
• Она штопает носки. = She is darning socks.

Yes, that is a natural English translation, even though the Russian literally says A thimble is needed in order to darn.

Russian нужен, чтобы... often expresses practical purpose, so in good English you might translate it as:

• A thimble is needed for darning.
• A thimble is used for darning.
• You use a thimble to darn.

The exact English wording can vary, while the Russian structure stays the same.

Yes. Russian can express purpose in more than one way.

Possible versions:

• Напёрсток нужен, чтобы штопать.
• Напёрсток нужен для штопанья.
• Напёрсток нужен для штопки.

These all relate to darning, but they feel slightly different:

• чтобы штопать = more verbal, to darn
• для штопанья / для штопки = more noun-based, for darning

The version with чтобы + infinitive is very common and straightforward for learners.

It is pronounced roughly na-PYOR-stak.

Important points:

• The ё is always stressed.
• So the stress is: напёрсток
• The letter ё sounds like yo.

This matters because е and ё are different letters in Russian, even though in everyday writing ё is sometimes replaced by е. In careful learning materials, you will often see ё written clearly.

Yes, it is a completely normal Russian sentence.

Russian often allows very compact statements, especially for:

• definitions
• instructions
• general truths
• descriptions of what objects are for

So Напёрсток нужен, чтобы штопать. is a neat, natural pattern:

• [thing] + нужен/нужна/нужно/нужны + чтобы + infinitive

For example:

• Карандаш нужен, чтобы рисовать.
• Ложка нужна, чтобы есть суп.
• Очки нужны, чтобы лучше видеть.

This pattern is very useful to learn.