Сьомий урок сьогодні.

Because Ukrainian often leaves out the present-tense form of to be.

So Сьомий урок сьогодні. is a normal complete sentence even though there is no spoken є.

Literally, you can think of it as something like:

Сьомий урок [є] сьогодні.

This is very common in Ukrainian. In the present tense, the verb to be is usually omitted unless you are making a special emphasis or using a different structure.

Сьомий is an ordinal number, meaning seventh.

In Ukrainian, ordinal numbers behave like adjectives, so they change to match the noun in:

• gender
• number
• case

Here it is masculine singular nominative because it matches урок, which is also masculine singular nominative.

So:

• сьомий урок = seventh lesson / seventh class period

Compare:

• сьома година = seventh hour
• сьоме питання = seventh question
• сьомі уроки = seventh lessons

This is just how the ordinal form of seven works in Ukrainian.

• сім = seven
• сьомий = seventh

The form is not built in a perfectly transparent way from the cardinal number, so it simply has to be learned as the standard ordinal form.

A learner will often just memorize pairs like these:

• один → перший
• два → другий
• три → третій
• чотири → четвертий
• сім → сьомий

So сьомий is normal and correct, even if it looks a bit less predictable than some other forms.

Урок is in the nominative singular form.

That is the basic dictionary form of the noun, and it fits here because the sentence is essentially naming what something is: the seventh lesson.

Also, урок is a masculine noun, which is why the ordinal before it is also masculine:

• сьомий урок

If the noun were feminine or neuter, the ordinal would change:

• сьома лекція = seventh lecture
• сьоме завдання = seventh task

So the form of сьомий is determined by урок.

Сьогодні means today, and here it functions as an adverb of time.

It tells you when the situation applies.

So the structure is basically:

• сьомий урок = the seventh lesson
• сьогодні = today

Together: the sentence says that this seventh lesson is the one that is happening today, or that today involves the seventh lesson, depending on context.

Because the meaning has already been shown to the learner, the key grammar point is simply that сьогодні is a time adverb and does not change form.

Yes, the word order can be different.

Ukrainian word order is more flexible than English word order. The ending position often gives extra focus or emphasis.

So Сьомий урок сьогодні. can sound like the speaker is highlighting today.

Other possible word orders include:

• Сьогодні сьомий урок.
• Сьомий сьогодні урок.

These can all be grammatical, but they may sound slightly different in emphasis or style.

A good rough guide:

• Сьогодні сьомий урок. = more neutral if you start with the time
• Сьомий урок сьогодні. = puts a bit more focus on today

Not always exactly.

Урок can mean:

• a lesson
• a school class period
• sometimes a teaching session

In school contexts, сьомий урок very often means the seventh class period.

So depending on context, English might translate it as:

• the seventh lesson
• the seventh period
• the seventh class

This is a good example of why one Ukrainian word does not always line up perfectly with one English word.

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

So урок can mean:

• a lesson
• the lesson

and context tells you which is meant.

That means a short sentence like Сьомий урок сьогодні. may sound a little more open-ended in isolation than an English sentence would. English usually has to choose between a and the, but Ukrainian does not.

A helpful approximate pronunciation is:

• сьо́мий ≈ SYO-myy
• уро́к ≈ u-ROK
• сього́дні ≈ syo-HOD-ni

A few pronunciation notes:

• The stress is on:
  • сьо́мий
  • уро́к
  • сього́дні
• сь is a soft consonant.
• Ukrainian г in сьогодні is pronounced like a voiced h, not like a hard English g.

So the whole sentence is approximately:

SYO-myy u-ROK syo-HOD-ni

That is only an approximation, but it is a useful starting point.

Not if you want the meaning seventh.

In Ukrainian, just like in English, there is a difference between:

• cardinal numbers: one, two, seven
• ordinal numbers: first, second, seventh

So:

• сім уроків = seven lessons
• сьомий урок = the seventh lesson

If you wrote 7 урок, that would not be the normal grammatical way to express seventh lesson. You need the ordinal form: сьомий.

Yes. Since it behaves like an adjective, it changes with gender, number, and case.

A few examples:

• сьомий урок = masculine nominative
• сьомого уроку = masculine genitive
• сьомому уроку = masculine dative
• сьома година = feminine nominative
• сьоме місце = neuter nominative
• сьомі уроки = plural nominative

So the form сьомий is not fixed. It is the correct form specifically for matching урок in this sentence.