Кілограм моркви коштує менше.

Because after a word of quantity like кілограм (a kilogram), Ukrainian normally uses the genitive case.

So:

• кілограм моркви = a kilogram of carrots / carrot
• not кілограм морква

This is very common in Ukrainian:

• кілограм яблук = a kilogram of apples
• літр молока = a liter of milk
• чашка чаю = a cup of tea

Here, моркви is the genitive singular form of морква.

Because the grammatical subject is кілограм, not моркви.

In other words, the sentence is built around:

• Кілограм ... коштує = A kilogram ... costs

So the verb agrees with кілограм, which is singular.

Compare:

• Кілограм моркви коштує менше. = A kilogram of carrots costs less.
• Морква коштує менше. = Carrots / carrot cost(s) less.

Even though English may focus on carrots, Ukrainian grammar here focuses on the kilogram.

Менше means less.

In this sentence, it means costs less or is cheaper in a price comparison.

So:

• коштує менше = costs less

It is the comparative form of мало / менше in the sense of quantity or amount, and with prices it naturally means for a lower price.

A useful comparison:

• дешево = cheaply
• дешевше = more cheaply / cheaper
• менше = less

With коштувати (to cost), Ukrainian very naturally says:

• коштує менше = costs less

Because Ukrainian, like English, can leave that understood from context.

Кілограм моркви коштує менше. can mean:

• a kilogram of carrots costs less than before
• a kilogram of carrots costs less than something else
• a kilogram of carrots costs less now

If you want to make the comparison explicit, you can add ніж (than):

• Кілограм моркви коштує менше, ніж кілограм картоплі.
• A kilogram of carrots costs less than a kilogram of potatoes.

Or:

• Кілограм моркви коштує менше, ніж торік.
• A kilogram of carrots costs less than last year.

So the short sentence is completely normal if the comparison is already clear.

Not in standard Ukrainian, no.

You need a verb or a different structure. The natural standard patterns are:

• Кілограм моркви коштує менше.
• Морква дешевша.
• Кілограм моркви є дешевшим. (more formal/bookish)

A common learner mistake is trying to copy English is cheaper too directly. In Ukrainian, with prices, коштує менше is very natural.

You may hear forms like коштує дешевше in speech, but many teachers and style guides prefer коштує менше.

In this kind of sentence, морква often works like a mass product noun, similar to how English can say carrot in a market/pricing context, but the natural translation is often carrots.

So:

• кілограм моркви = a kilogram of carrots

Ukrainian often uses the singular dictionary form for food items or produce in these quantity expressions, even when English prefers a plural translation.

Similar examples:

• кілограм картоплі = a kilogram of potatoes
• кілограм цибулі = a kilogram of onions

So don’t worry if the Ukrainian looks singular while English sounds more natural in the plural.

Yes. Ukrainian word order is flexible, though the neutral order here is:

• Кілограм моркви коштує менше.

You could also say:

• Моркви кілограм коштує менше.
• Менше коштує кілограм моркви.

But those versions change the emphasis.

Very roughly:

• Кілограм моркви коштує менше. = neutral
• Менше коштує кілограм моркви. = emphasizes costs less
• Моркви кілограм... = marked, often used for contrast or special focus

As a learner, the original order is the safest and most natural.

Here are the base forms:

• кілограм → dictionary form: кілограм
• моркви → dictionary form: морква
• коштує → dictionary form: коштувати (to cost)
• менше → comparative form meaning less

A quick grammar breakdown:

• кілограм — masculine noun, nominative singular
• моркви — genitive singular
• коштує — 3rd person singular present tense
• менше — comparative adverb

A simple pronunciation guide:

• Кілограм → kee-loh-HRAM
• моркви → MOR-kvy
• коштує → KOSH-too-ye
• менше → MEN-she

Put together:

• Кілограм моркви коштує менше.
• kee-loh-HRAM MOR-kvy KOSH-too-ye MEN-she

A few helpful notes:

• г in Ukrainian is usually like a soft h sound, so кілограм is not exactly like Russian-style hard g
• є in коштує sounds like ye
• ш in менше is like English sh

You just replace кілограм with another quantity word, and the product noun usually stays in the genitive.

Examples:

• Пів кілограма моркви коштує менше. = Half a kilogram of carrots costs less.
• Два кілограми моркви коштують менше. = Two kilograms of carrots cost less.
• Три кілограми моркви коштують менше. = Three kilograms of carrots cost less.

Notice that the verb changes with the subject:

• кілограм ... коштує = singular
• два / три кілограми ... коштують = plural

So the quantity word controls the verb agreement.