Продавець ставить ваги на прилавок.

Продавець is the subject of the sentence, so it is in the nominative case. It means seller / shop assistant / salesperson.

You can tell it is the subject because the verb ставить is in the 3rd person singular, matching продавець.

Because ваги is not the subject. The subject is продавець.

So the structure is:

• Продавець = the seller
• ставить = puts / is putting
• ваги = the scales
• на прилавок = onto the counter

The verb agrees with продавець, not with ваги.

Here ставить means to put, to set, or to place something in an upright or set position.

In this sentence, it means the seller is putting / setting the scales onto the counter.

A useful thing to know: Ukrainian present tense can often translate as either:

• puts
• is putting

depending on context.

So Продавець ставить ваги на прилавок can mean either:

• The seller puts the scales on the counter
• The seller is putting the scales on the counter

Yes, very much so.

Ваги means scales and is normally used as a plural-only noun. This is similar to English words like:

• scales
• scissors
• glasses

Even if it refers to one object, the noun is grammatically plural.

Also, do not confuse it with вага, which means weight, not a scale.

So:

• вага = weight
• ваги = scales

Because this sentence describes movement toward a destination.

With на, Ukrainian often uses:

• accusative for motion onto/to
• locative for location on/in

So:

• на прилавок = onto the counter
• на прилавці = on the counter (already there)

Compare:

• Продавець ставить ваги на прилавок. = The seller puts the scales onto the counter.
• Ваги стоять на прилавці. = The scales are standing on the counter.

This is one of the most important case patterns in Ukrainian.

It is in the accusative case, because it follows на with the meaning of movement onto something.

For an inanimate masculine noun like прилавок, the accusative singular is the same as the nominative singular. So the form stays прилавок.

That is why you see:

• nominative: прилавок
• accusative: прилавок

But the function is different.

Прилавок usually means a counter or shop counter, especially the kind used in a store or market.

So in this sentence, на прилавок means onto the shop counter.

It is more specific than a general word like table.

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

The neutral order here is:

• Продавець ставить ваги на прилавок.

But other orders are possible, for example:

• Ваги продавець ставить на прилавок.
• На прилавок продавець ставить ваги.

These versions can sound more emphatic or shift the focus.

Even so, the original sentence is the most straightforward and natural basic order for a learner.

Because Ukrainian has no articles.

So продавець can mean:

• a seller
• the seller

and прилавок can mean:

• a counter
• the counter

You understand whether it is a or the from context.

That is completely normal in Ukrainian.

Yes, ставить is imperfective.

That means it presents the action as:

• ongoing,
• repeated,
• habitual,
• or simply not viewed as completed.

So in context it can mean:

• is putting
• puts
• usually puts

The perfective partner is often поставити, which focuses on the completed result:

• Продавець поставив ваги на прилавок. = The seller put / has put the scales on the counter.

So aspect matters a lot in Ukrainian.

Sometimes yes, but ставить is a very natural choice here.

Ukrainian often distinguishes between different kinds of putting:

• ставити = put something standing / set something down
• класти = put something lying down
• вішати = hang something

Since ваги are something you would normally set down on a counter, ставить is the expected verb.

So this sentence sounds natural and idiomatic.