Бабушка штопает носок.

Бабушка is the subject of the sentence, so it is in the nominative case.

• бабушка = grandmother / grandma
• nominative is the basic dictionary form used for the subject

So in Бабушка штопает носок, бабушка is the person doing the action.

Штопает comes from the infinitive штопать, which means to darn or to mend clothing by sewing over a hole or worn spot.

So this is more specific than just to sew.

• штопать = to darn, to mend
• шить = to sew

If a grandmother is repairing a sock with needle and thread, штопать is the natural verb.

Because штопает is the 3rd person singular present tense form of штопать.

The subject бабушка is:

• she
• singular

So the verb must mean she is darning / she darns.

A short conjugation:

• я штопаю = I darn
• ты штопаешь = you darn
• он / она штопает = he / she darns
• мы штопаем = we darn
• вы штопаете = you darn
• они штопают = they darn

It is in the accusative. The important point is that for many masculine inanimate nouns, the accusative singular looks exactly the same as the nominative singular.

So:

• nominative: носок
• accusative: носок

That is why the object does not visibly change here.

Compare:

• Я вижу стол. = I see a table.
  (стол is also unchanged in the accusative because it is masculine and inanimate.)

You know from sentence structure and meaning.

In Бабушка штопает носок:

• бабушка is the person doing the action, so it is the subject
• носок is the thing being repaired, so it is the direct object

Even though носок looks the same as nominative, its role in the sentence is accusative.

Russian often relies on a combination of:

• verb meaning
• context
• case endings
• word order

Here, the meaning makes the roles clear.

It can mean either, depending on context.

Russian present tense often covers both:

• she is darning a sock
• she darns a sock

In many simple textbook sentences, English often uses the continuous form:

• Grandma is darning a sock

But Russian itself does not have a separate continuous tense like English.

Russian does not have articles.

So носок can mean:

• a sock
• the sock

The exact meaning depends on context.

Likewise, бабушка can mean:

• grandma
• the grandmother
• sometimes just an old woman, depending on context

English must choose an article, but Russian does not.

Yes. Russian word order is more flexible than English because case endings help show grammatical roles.

The basic neutral order here is:

• Бабушка штопает носок.

But you could also hear:

• Носок штопает бабушка.
• Штопает бабушка носок.

These versions may sound more marked and can shift the emphasis.

For example:

• Бабушка штопает носок. = neutral statement
• Носок штопает бабушка. = emphasis on the sock
• Штопает бабушка носок. = more stylistic or context-driven emphasis

For beginners, it is best to learn the neutral order first.

The stress is:

• ба́бушка
• што́пает
• носо́к

A simple pronunciation guide:

• ба́бушка ≈ BA-bush-ka
• што́пает ≈ SHTO-pa-yet
• носо́к ≈ na-SOK or no-SOK depending on how closely you approximate Russian unstressed vowels

A rough full pronunciation:

• BA-bush-ka SHTO-pa-yet na-SOK

The stressed syllables are very important in Russian, so it is worth learning them early.

Штопать is the imperfective verb. Imperfective is commonly used for:

• an action in progress
• a repeated or habitual action
• a general statement of what someone does

So Бабушка штопает носок naturally describes the process of darning or the activity itself.

If you wanted a perfective idea such as will mend / finish mending, Russian would usually use a different verb.

Yes. Бабушка most often means grandmother / grandma, but in some contexts it can also mean an elderly woman.

So depending on the situation, it might mean:

• Grandma is darning a sock
• The old lady is darning a sock

If this is a family-context textbook sentence, grandmother is probably the intended meaning.

Both can relate to fixing something, but they are not the same.

• штопать = to darn, specifically repair fabric by stitching over damage
• чинить = to repair, fix, mend in a broader sense

So for a sock with a hole, штопать носок is very natural and specific.

You could think of it this way:

• чинить is more general
• штопать is the exact action used for clothing or fabric repair

Yes. In the plural, the object form would change.

• singular: Бабушка штопает носок.
• plural: Бабушка штопает носки.

Here носки is the plural form of носок.

This is a useful reminder that case and number changes do often show up clearly, even if the singular accusative here happens to look unchanged.

The dictionary forms are:

• бабушка = grandmother, grandma
• штопать = to darn, to mend
• носок = sock

In the sentence:

• бабушка is already in its dictionary form
• штопает is a conjugated form of штопать
• носок is also in a form that looks like its dictionary form, even though here it functions as the accusative object