Вилиця під оком.

Not quite.

• вилиця = cheekbone
• щока = cheek (the softer, fleshy part)

So this sentence is talking about the bone/upper cheek area under the eye, not the ordinary cheek in general.

In Ukrainian, the present-tense to be is usually omitted.

So:

• Вилиця під оком. = The cheekbone is under the eye.

You can add a fuller verb in some contexts, for example:

• Вилиця розташована під оком. = The cheekbone is located under the eye.

But in simple descriptions, Ukrainian normally leaves є out.

Вилиця is in the nominative singular.

It is the main noun of the sentence, the thing being described. It is also:

• feminine
• singular

That means adjectives agreeing with it would also be feminine singular, for example:

• ліва вилиця = the left cheekbone

Because під can take different cases depending on meaning.

With location:

• під + instrumental
• під оком = under the eye

With movement toward a position under something:

• під + accusative
• під око = to under the eye / under the eye area (much less common in this exact body-part context)

This sentence describes a static location, so Ukrainian uses the instrumental: оком.

Because оком is the instrumental singular form of око.

A few useful singular forms are:

• око — nominative
• ока — genitive
• оку — dative
• око — accusative
• оком — instrumental

So after під for location, you need the instrumental form:

• під оком

Also note that око has an irregular plural:

• очі = eyes

Ukrainian has no articles like English a / an / the.

So Вилиця під оком can literally be interpreted from context, and English usually adds the naturally:

• The cheekbone is under the eye.

In anatomy/body-part descriptions, English usually wants the, but Ukrainian does not need any word for it.

Yes. Ukrainian word order is fairly flexible.

The given order:

• Вилиця під оком.

is a neutral way to say it.

You could also say:

• Під оком вилиця.

But that would sound more marked, as if you are emphasizing the location under the eye.

So for a basic learner sentence, Вилиця під оком is the most straightforward order.

It sounds a bit like a label or simple anatomical description, which is normal in learning materials.

In everyday speech, a fuller sentence might sound more natural, for example:

• Вилиця розташована під оком.
• Під оком розташована вилиця.

But the short version Вилиця під оком is completely understandable and very common in vocabulary-style contexts.

The ending -ця is pronounced roughly like tsya.

Break it down like this:

• ц = ts as in cats
• я after a consonant makes it sound softer and adds an a-like sound

So вилиця is approximately:

• vy-ly-tsya

And the whole phrase is roughly:

• vy-ly-tsya pid o-kom

Try to keep the vowels clear; Ukrainian vowels are usually pronounced more distinctly than in English.

You would say:

• під очима = under the eyes

This uses the plural of око:

• очі = eyes
• очима = instrumental plural

So:

• під оком = under the eye
• під очима = under the eyes

This is a useful pair to remember because око has an irregular plural.