Нашому дядькові сорок років.

Because Ukrainian usually expresses age with a dative + number + years structure.

So Нашому дядькові сорок років is literally something like:

To our uncle [there are] forty years.

In natural English, that becomes Our uncle is forty years old.

The person whose age is being stated is typically put in the dative, not the nominative.

Yes, in a sense.

Ukrainian often leaves out the present-tense verb to be. So there is no word for is in this sentence.

That is completely normal. The sentence is understood as:

Нашому дядькові [є] сорок років

but є is usually omitted.

Because numerals in Ukrainian affect the form of the noun that follows them.

With 40, the noun рік takes the genitive plural form:

• 1 рік
• 2, 3, 4 роки
• 5+ років

So:

• сорок років = forty years

That is why років is correct here.

In this sentence, сорок is the numeral used to state age, and it appears in its basic form.

The main grammatical change is happening in:

• the person: нашому дядькові → dative
• the noun рік → років

The numeral сорок itself stays сорок here.

Нашому means to our or our in this dative structure.

It agrees with дядькові, which is:

• masculine
• singular
• dative

So the possessive word наш changes to match:

• наш дядько = our uncle
• нашому дядькові = to our uncle

The ending -ому is the dative singular masculine/neuter ending for this kind of word.

Yes, both are possible.

For many masculine nouns in the dative singular, Ukrainian allows two forms:

• дядькові
• дядьку

So you can say:

• Нашому дядькові сорок років
• Нашому дядьку сорок років

Both are grammatical.
-ові / -еві / -єві forms often sound a bit fuller or more formal/literary, while -у / -ю forms are also common.

No, not for age.

That sounds incomplete or unnatural as an age statement, because Ukrainian normally uses the dative for the person in this pattern.

So for age, you want:

• Нашому дядькові сорок років

not:

• Наш дядько сорок років

This is generally not the standard Ukrainian way to express age.

The normal Ukrainian pattern is:

• Йому сорок років
• Нашому дядькові сорок років

Using мати (to have) for age is often felt to be nonstandard or influenced by other languages.

So the safest and most idiomatic choice is the dative pattern.

A very literal translation is:

To our uncle [there are] forty years.

That sounds unnatural in English, but it helps show the Ukrainian grammar.

The normal English meaning is:

Our uncle is forty years old.

Yes. Ukrainian word order is flexible.

The neutral order here is:

• Нашому дядькові сорок років

But other orders are possible for emphasis, for example:

• Сорок років нашому дядькові

That might emphasize forty years more strongly.

Still, the original order is a very natural, standard way to say it.

In full, careful speech, років is normally included:

• Нашому дядькові сорок років

In conversation, people may sometimes omit років if the context clearly shows they are talking about age:

• Йому сорок

But for learners, it is best to use the full form with років.

The same structure is used for other numbers too:

• Нашому дядькові один рік = Our uncle is one year old
• Нашому дядькові два роки = Our uncle is two years old
• Нашому дядькові три роки = Our uncle is three years old
• Нашому дядькові чотири роки = Our uncle is four years old
• Нашому дядькові п’ять років = Our uncle is five years old

So the main thing to watch is the form of рік:

• 1 → рік
• 2–4 → роки
• 5+ → років