Скільки років Вашому синові?

Word by word, it is:

• Скільки = how many
• років = years
• Вашому = to your / for your (formal, dative form)
• синові = son in the dative singular

So the literal structure is roughly How many years to your son?

That sounds strange in English, but it is the normal Ukrainian way to ask someone’s age.

Because скільки usually requires the noun after it to be in the genitive plural.

Here:

• рік = year
• роки = years (nominative plural)
• років = of years / genitive plural

So:

• Скільки років? = How many years?

This is also part of the normal age pattern in Ukrainian. Compare:

• один рік = one year
• два роки = two years
• три роки = three years
• чотири роки = four years
• п’ять років = five years
• десять років = ten years

After скільки, Ukrainian uses років.

They are both in the dative case.

Ukrainian often expresses age with the pattern:

[someone in dative] + [number] + років

Literally, it is like saying to someone, there are X years.

So:

• Вашому = to your (dative singular masculine)
• синові = to the son / for the son (dative singular)

The adjective has to agree with the noun, so both words appear in the dative singular.

The capital letter shows polite/formal address.

In Ukrainian, Ви, Ваш, and related forms can be capitalized when you are politely addressing one person, especially in writing.

So:

• Вашому синові = to your son in a polite/formal sense
• твоєму синові = to your son in an informal sense

In speech, you would not hear the capital letter, of course. It is only a writing convention.

The informal version is:

Скільки років твоєму синові?

Here:

• твоєму = to your (informal singular)

Everything else stays the same.

So the contrast is:

• Скільки років Вашому синові? = formal/polite
• Скільки років твоєму синові? = informal

Because Ukrainian normally does not use a present-tense verb here.

English says:

• How old is your son?

But Ukrainian uses a different structure and usually omits the present-tense to be.

So you do not need a word like is in this sentence.

This is very common in Ukrainian. The idea of is/are in the present tense is often left unspoken when it is clear from the context.

Yes. Both are correct dative singular forms of син.

So you can say:

• Скільки років Вашому синові?
• Скільки років Вашому сину?

Both mean the same thing.

Learners will often see both -ові / -еві / -єві endings and shorter -у / -ю endings in the dative singular. With син, both синові and сину are standard.

The given word order is the most neutral and standard:

Скільки років Вашому синові?

Ukrainian word order is fairly flexible, so other versions are possible, but they may sound more marked, conversational, or emphatic.

For example, you may also hear:

• Вашому синові скільки років?
• Скільки Вашому синові років?

These are not wrong, but the original sentence is the safest version for a learner.

A full answer could be:

• Моєму синові десять років. = My son is ten years old.

A shorter answer:

• Йому десять років. = He is ten years old.

An even shorter, very natural answer:

• Йому десять. = He’s ten.

Notice the same age pattern:

• йому один рік = he is one year old
• йому два роки = he is two
• йому п’ять років = he is five

A helpful stress pattern is:

Скі́льки ро́ків Ва́шому сино́ві?

A rough English-style approximation is:

SKEEL-ky RO-kiv VA-sho-mu sy-NO-vi?

A few pronunciation notes:

• і sounds like ee in see
• и is not exactly English ee; it is a shorter, more central vowel
• ль in Скільки is soft
• в in Вашому is a normal v sound

If you want to sound natural, getting the stresses right helps a lot:

• Скі́льки
• ро́ків
• Ва́шому
• сино́ві