Щенок тянет поводок, когда видит кошку.

Щенок is the nominative singular form, because it is the subject of the sentence — the one doing the action.

• щенок = puppy
• It is a masculine singular noun

So in Щенок тянет поводок, щенок is simply the puppy as the subject.

Тянуть is the dictionary form of the verb, meaning to pull.

In the sentence, we need the verb to match he/she/it in the present tense, so it becomes:

• я тяну = I pull
• ты тянешь = you pull
• он / она / оно тянет = he / she / it pulls

Since щенок is a singular subject and can be understood as it, Russian uses тянет.

It is in the accusative — but for many masculine inanimate nouns, the accusative singular looks exactly like the nominative singular.

So:

• поводок = leash (nominative)
• поводок = leash (accusative, because it is inanimate)

That is why the form does not visibly change.

Compare:

• Я вижу поводок = I see a leash

But with an animate masculine noun, the accusative would usually look different.

Because кошка is the direct object of видит and it is a feminine noun, so it changes to the accusative singular.

Pattern:

• nominative: кошка
• accusative: кошку

This is a very common feminine pattern:

• мама → маму
• девушка → девушку
• кошка → кошку

So видит кошку means sees a cat.

Russian often omits subject pronouns when the subject is clear from context.

In English, we usually say:

• The puppy pulls the leash when it sees a cat.

In Russian, once щенок has already been introduced as the subject, the second clause can simply say:

• когда видит кошку

The subject is understood to be the same: the puppy.

If needed for emphasis or clarity, Russian could also say:

• Щенок тянет поводок, когда он видит кошку.

But in normal speech, leaving out он is very natural.

Because когда видит кошку is a subordinate clause.

Russian normally uses a comma to separate a main clause from a subordinate clause:

• Щенок тянет поводок, когда видит кошку.

This is standard punctuation in Russian.

It can suggest either, depending on context.

In this sentence, because both verbs are in the present tense and the idea is general/habitual, English often understands it as:

• when
• or more naturally, whenever

So the sentence describes a repeated situation: each time the puppy sees a cat, it pulls the leash.

The verbs тянуть and видеть are imperfective, which fits this sentence because it describes a habitual, repeated, or general action.

The idea is not:

• one completed act of pulling
• one completed act of seeing

Instead, it is a general behavior:

• The puppy pulls the leash when it sees a cat.

Imperfective verbs are very common for this kind of repeated action.

In Russian, the present tense of an imperfective verb can often correspond to simple present English:

• видит = sees

English sometimes distinguishes between sees and is seeing, but Russian usually does not make that same contrast in the present tense in the same way.

Here, the natural translation is sees, because the sentence describes normal repeated behavior.

Because the verb is видеть and its present-tense forms follow the pattern of a second-conjugation verb:

• я вижу
• ты видишь
• он / она / оно видит
• мы видим
• вы видите
• они видят

So видит is simply the correct 3rd person singular form.

This is a good verb to memorize, because its present forms are a little less predictable than some beginners expect from the infinitive -еть.

Yes, absolutely.

That version is also correct:

• Когда щенок видит кошку, он тянет поводок.

Russian word order is more flexible than English word order. Both versions mean essentially the same thing.

The difference is mainly in focus:

• Щенок тянет поводок, когда видит кошку.
  starts with the main action
• Когда щенок видит кошку, он тянет поводок.
  starts with the condition/situation

Both are natural.

Yes, literally тянет поводок means pulls the leash.

In English, we often say:

• pulls the leash
• pulls on the leash

Russian commonly uses the direct object without a preposition here:

• тянуть поводок

So even if English prefers pull on the leash in some contexts, Russian naturally says тянуть поводок.

Поводок is masculine.

That matters because masculine nouns have their own case patterns. In this sentence, since поводок is inanimate, its accusative singular is the same as the nominative:

• nominative: поводок
• accusative: поводок

So the gender helps determine how the noun behaves grammatically.

Yes. Russian does not have articles like a and the, so кошку can mean either:

• a cat
• the cat

The context tells you which is more natural.

In a general sentence like this, English usually says a cat:

• The puppy pulls the leash when it sees a cat.

But Russian itself does not mark that difference with an article.