Десятий урок короткий.

In Ukrainian, the verb to be is usually left out in the present tense.

So:

• Десятий урок короткий. literally looks like Tenth lesson short but means The tenth lesson is short.

This is completely normal in Ukrainian.
If you want to talk about the past or future, forms of бути are used more clearly.

For example:

• Урок був короткий. = The lesson was short.
• Урок буде короткий. = The lesson will be short.

Десять means ten.

But десятий means tenth.

English has the same distinction:

• ten = a cardinal number
• tenth = an ordinal number

In this sentence, десятий describes урок as a position in a sequence, so it must be an ordinal number:

• десятий урок = the tenth lesson

Grammatically, ordinal numbers in Ukrainian behave like adjectives, not like basic numbers.

Because both words are in the masculine singular nominative form.

Here is what each word is doing:

• десятий describes урок
• короткий also matches урок, because it tells us what the lesson is like

The noun урок is:

• masculine
• singular
• nominative case

So both adjectives must agree with it.

That is why you get:

• десятий урок
• урок короткий

If the noun were feminine, the forms would change. For example:

• десята сторінка коротка would not work semantically very well, but grammatically it shows the agreement pattern:
  • десята = feminine
  • коротка = feminine

It is in the nominative case.

This sentence is a simple statement about the subject:

• Десятий урок = the subject
• короткий = what is being said about the subject

So the noun appears in its basic dictionary form, the nominative.

A good way to think about it is:

• Who/what is short? → Десятий урок

That is why урок is nominative, and the words agreeing with it are nominative too.

In Ukrainian, when an adjective is used after the subject in a sentence like X is Y, it often still agrees with the subject in gender, number, and case.

So:

• урок = masculine singular nominative
• короткий must match that

This is why you see:

• урок короткий not just some unchanged form of short

English adjectives do not change form:

• short lesson
• the lesson is short

But Ukrainian adjectives do change:

• короткий урок
• урок короткий

Both короткий forms are masculine singular nominative here.

Yes, Ukrainian word order is more flexible than English word order.

The most neutral version here is:

• Десятий урок короткий.

But you could also say:

• Урок короткий. = The lesson is short.
• Десятий урок — короткий. = slightly more emphatic or contrastive
• Короткий десятий урок. = this sounds more like a short tenth lesson, where both words directly describe the noun, not a normal neutral statement

So although word order can change, it may affect:

• emphasis
• style
• whether something sounds like a full statement or just a noun phrase

For a beginner, Десятий урок короткий is a good standard pattern.

Ukrainian does not have articles like a/an and the.

So:

• урок can mean a lesson or the lesson
• the exact meaning depends on context

In your sentence, English naturally translates it as The tenth lesson is short, because tenth lesson usually refers to a specific one.

So Ukrainian expresses this idea without an article.

Yes.

десятий урок means the tenth lesson and functions as a complete noun phrase:

• десятий = adjective-like ordinal
• урок = noun

Together they form the subject of the sentence.

Then короткий tells us something about that subject.

So the sentence structure is basically:

• [десятий урок] [короткий]
• [the tenth lesson] [is short]

Yes, very much so.

Ordinal numbers such as:

• перший = first
• другий = second
• десятий = tenth

decline like adjectives and agree with the noun they modify.

That means they change for:

• gender
• number
• case

For example:

• десятий урок = masculine singular
• десята сторінка = feminine singular
• десяте вікно = neuter singular
• десяті уроки = plural

This is why десятий looks more like an adjective than like the number десять.

Because урок is a masculine noun in Ukrainian.

One clue is its dictionary form: it ends in a consonant, which is very often masculine in Ukrainian.

Since урок is masculine, words that agree with it must also be masculine:

• десятий урок
• урок короткий

If the noun had a different gender, the adjective forms would change.

For example:

• masculine: короткий урок
• feminine: коротка лекція
• neuter: коротке завдання

So the endings in the sentence are determined by the gender of урок.

Possibly, yes, depending on context.

The word урок can mean:

• lesson
• class period
• sometimes school class/session

So the exact English translation may vary a little depending on the situation.

But grammatically the sentence works the same way in all of those interpretations:

• Десятий урок короткий.

So if you already know the intended meaning from context, the main thing to focus on is the grammar:

• ordinal + noun
• no present-tense is
• adjective agreement with a masculine singular subject