Його підборіддя мокре.

Here його means his.

In Ukrainian, його can be:

• a pronoun form meaning him
• a possessive form meaning his

In Його підборіддя мокре, it comes before a noun, so it is understood as the possessive his: his chin.

No. As a possessive, його does not change for the gender or number of the thing owned.

So you get:

• його брат = his brother
• його сестра = his sister
• його підборіддя = his chin
• його руки = his hands

This is different from adjectives, which do change.

Because підборіддя is a neuter singular noun, and the adjective must agree with it.

The forms are:

• мокрий = masculine
• мокра = feminine
• мокре = neuter
• мокрі = plural

So:

• ніс мокрий = the nose is wet
• борода мокра = the beard is wet
• підборіддя мокре = the chin is wet

Because in Ukrainian, not all nouns ending in -я are feminine. Some are neuter.

Підборіддя is one of those neuter nouns. Other common neuter nouns with similar endings include:

• життя
• питання
• ім'я

So even though the ending may look unusual at first, підборіддя is grammatically neuter.

It is in the nominative singular.

In this sentence, підборіддя is the subject: the thing being described as wet. Because it is nominative singular neuter, the adjective is also nominative singular neuter: мокре.

Because Ukrainian usually omits the verb to be in the present tense in simple statements like this.

So:

• Його підборіддя мокре literally looks like His chin wet
• but naturally means His chin is wet

This is very normal Ukrainian grammar.

Because here мокре is the predicate adjective: it tells you what the chin is like.

So:

• Його підборіддя мокре = His chin is wet

If you move the adjective before the noun:

• Його мокре підборіддя

that becomes a noun phrase meaning:

• his wet chin

So the word order helps show whether you have a full sentence or just a noun phrase.

Yes, absolutely. That is also natural Ukrainian.

У нього мокре підборіддя literally means something like At him, the chin is wet, but in natural English it comes out as:

• He has a wet chin
• His chin is wet

The version with його підборіддя focuses more directly on his chin as the subject. The у нього pattern is a very common way to express possession.

By itself, the form can be ambiguous, but the sentence structure usually makes the meaning clear.

Compare:

• Я бачу його = I see him
• Його підборіддя мокре = His chin is wet

When його comes directly before a noun, it is normally understood as possessive: his.

A helpful rough guide is pid-bo-RID-dya.

A few points:

• the stress is on -рі-
• і sounds like ee in see
• ддя is soft, something like ddya
• say it slowly first: під-бо-рід-дя

Also, the double дд is not silent; it gives the ending a slightly lengthened sound.

A rough guide is yo-HO.

Two useful notes:

• the stress is on the last syllable
• Ukrainian г is usually pronounced like a voiced h sound, not like English g

So його does not sound like a hard g word.