Это обязательный урок.

This is a mandatory lesson.

Breakdown of Это обязательный урок.

• это: this
• урок: the lesson
• обязательный: required

Questions & Answers about Это обязательный урок.

Why is it Это обязательный урок, and not Этот обязательный урок or Он обязательный урок?

Russian makes a clear distinction between:

1. Это + noun

   • Functions like “this is / it is”.
   • Used to identify or classify something.
   • Это обязательный урок. = This is a mandatory lesson. / It’s a mandatory lesson.

2. Этот + noun

   • Means “this [specific] …” and directly modifies the noun.
   • Этот урок обязательный. = This lesson is mandatory.
     
     • Here этот is just a determiner (“this”), not “this is”.

3. Он

   • Refers back to a masculine noun already mentioned (like урок).
   • You can say: Урок обязательный. Он обязательный. = The lesson is mandatory. It is mandatory.
   • But Он обязательный урок is wrong: Russian does not do “He is a mandatory lesson” the way English might say “He is a teacher.”

So in Это обязательный урок, это is not “this lesson” grammatically; it’s “this/it” used in the pattern “this is X”.

Why is there no word for “is”? Why don’t we say Это есть обязательный урок?

In Russian, the present-tense verb “to be” (быть) is usually omitted in simple “X is Y” sentences.

• English: This is a mandatory lesson.
• Russian: Это обязательный урок. (no есть)

Using есть here — Это есть обязательный урок — sounds unnatural in modern Russian, except in very formal, logical, or philosophical speech. For everyday language, you just say:

• Он врач. = He is a doctor.
• Это проблема. = This is a problem.
• Это обязательный урок. = This is a mandatory lesson.

What cases are used in Это обязательный урок? Why doesn’t anything change case?

All the meaningful words here are in the nominative case:

• урок – nominative singular, masculine
• обязательный – nominative singular, masculine (agrees with урок)
• это – indeclinable form used as a pronoun (“this / it”)

In a basic “X is Y” sentence of identity or classification, Russian normally uses the nominative for both sides:

• Это урок. – This is a lesson.
• Он учитель. – He is a teacher.
• Она студентка. – She is a student.
• Это обязательный урок. – This is a mandatory lesson.

So nothing goes into accusative, genitive, etc.; it’s just subject + predicate noun/adjective in nominative.

Why does обязательный end with -ый here? How does gender agreement work?

Обязательный is an adjective and must agree with the noun урок in:

• gender – урок is masculine
• number – singular
• case – nominative

Masculine nominative singular adjectives typically end in -ый or -ий, so we get:

• обязательный урок – mandatory lesson
• интересный урок – interesting lesson
• новый урок – new lesson

Compare with other genders:

• обязательная лекция (feminine, nom. sg.) – mandatory lecture
• обязательное задание (neuter, nom. sg.) – mandatory task
• обязательные уроки (plural, nom.) – mandatory lessons

So обязательный is in its masculine nominative singular form to match урок.

What is the difference between обязательный, обязательно, and обязателен?

They are related but grammatically different:

1. обязательный – full-form adjective

   • Describes a noun:
     • обязательный урок – a mandatory lesson
     • обязательный предмет – a required subject

2. обязательно – adverb or short-form neuter adjective
   a) As an adverb: “necessarily, by all means, definitely”

   • Я обязательно приду. – I will definitely come.
     b) As a short-form neuter adjective, often used like a general statement:
   • Это обязательно. – This is mandatory / It’s a must.

3. обязателен / обязательна / обязательно / обязательны – short-form adjective (gender/number-specific)

   • Often used as a predicate:
     • Этот урок обязателен. – This lesson is mandatory.
     • Эта лекция обязательна. – This lecture is mandatory.
     • Посещение обязательно. – Attendance is mandatory.

In your sentence, you are modifying a noun directly, so you use the full adjective: обязательный урок.

Is there a difference between Это обязательный урок and Этот урок обязательный?

Both are correct, but they have slightly different structure and nuance:

1. Это обязательный урок.

   • Pattern: Это + [adjective + noun]
   • Feels like identification/classification:
     
     • “This is a mandatory lesson (that kind of lesson).”

2. Этот урок обязательный.

   • Pattern: [demonstrative + noun] + predicate adjective
   • Closer to “This lesson is mandatory”, often contrasting with others:
     
     • “This lesson (as opposed to other ones) is mandatory.”

In many real-life contexts, they can be used almost interchangeably, but:

• If you’re introducing what something is: Это обязательный урок.
• If you’re talking about a specific known lesson and stressing its property (being mandatory): Этот урок обязательный.

How do I make this sentence plural, like “These are mandatory lessons”?

You have two main patterns:

1. Это обязательные уроки.

   • Literally: “This is mandatory lessons,” but in Russian это is used for both “this is” and “these are.”
   • обязательные – plural nominative to agree with уроки.
   • Very natural as a neutral statement: Это обязательные уроки. – These are mandatory lessons.

2. Эти уроки обязательные.

   • эти уроки – “these lessons” (demonstrative modifying the noun)
   • обязательные – predicate adjective, plural nominative
   • Meaning: “These lessons are mandatory (as opposed to other lessons).”

So:

• Это обязательные уроки. – These are mandatory lessons.
• Эти уроки обязательные. – These lessons are mandatory.

Can I say Урок обязательный without это? How does that sound?

Yes, you can, but the feel is different:

• Урок обязательный.
  
  • Literally: “The lesson is mandatory.”
  • Sounds like a descriptive or explanatory sentence, often after the lesson is already known from context.
  • Could be part of a longer explanation:
    • Урок обязательный, поэтому все должны приходить.
      – The lesson is mandatory, so everyone must come.

Compare:

• Это обязательный урок. – Introducing or classifying: “This is a mandatory lesson.”
• Урок обязательный. – Describing a known lesson: “The lesson is mandatory.”

Both are grammatically fine; which one you use depends on context and emphasis.

How do I say this in the past or future? For example, “That was a mandatory lesson” or “That will be a mandatory lesson”?

Use forms of быть (to be) in the past or future:

1. Past:

   • Это был обязательный урок. – That was a mandatory lesson.
     
     • был – masculine past of быть, agreeing with урок.

2. Future:

   • Это будет обязательный урок. – That will be a mandatory lesson.
     
     • будет – 3rd person singular future of быть.

You can also change the structure slightly:

• Урок был обязательным. – The lesson was mandatory.
  
  • Here обязательным is in the instrumental case, often used in predicate position with был / будет to describe a state or quality.

All of these are natural; the choice is mostly about style and what you want to emphasize (the identity “this is that kind of lesson” vs. the property “the lesson was / will be mandatory”).

How is Это обязательный урок pronounced, and where is the stress?

Stresses:

• Э́то обяза́тельный уро́к.

Pronunciation (approximate):

• Э́то – [É-ta], stress on Э.
• обяза́тельный – [a-bya-ZÁ-til-nyi], stress on the а after з.
• уро́к – [u-RÓK], stress on о́.

So you get:

• [ˈetə ɐbʲɪˈzatʲɪlʲnɨj ʊˈrok]

Key points:

• Unstressed о is reduced and sounds more like a or ɐ.
• Make sure to stress за́ in обяза́тельный and ро́к in уро́к; wrong stress (for example обязате́льный) will sound foreign.

Is обязательный only used for school lessons, or more generally? What kinds of things can be обязательный?

Обязательный is used broadly for anything required / compulsory / obligatory. Common collocations include:

• обязательный предмет – compulsory subject (in school/university)
• обязательный экзамен – required exam
• обязательное условие – necessary / mandatory condition
• обязательная программа – compulsory program
• обязательное посещение – mandatory attendance
• обязательный платеж – obligatory payment (e.g. fees, taxes)

So обязательный урок fits a general pattern: an event or element that is not optional but required by some rule, program, or authority.