Этот бесплатный урок интересный.

In Russian, in the present tense, the verb “to be” (быть) is normally left out in sentences like this.

• English: This free lesson is interesting.
• Russian: Этот бесплатный урок интересный.
  (literally: This free lesson interesting.)

So there is an understood “is” between урок and интересный, but it is not spoken or written:

• Этот бесплатный урок [есть] интересный. – the есть is usually omitted in modern Russian.

Both этот and это can translate as “this”, but they agree with gender and number:

• этот – masculine singular (for masculine nouns)
• эта – feminine singular
• это – neuter singular
• эти – plural

The noun урок (lesson) is masculine, so you must say:

• этот урок – this lesson

If the noun were neuter, e.g. занятие (class, session), you would say:

• это занятие – this class

Those are adjectives agreeing with the noun урок in:

• gender: masculine
• number: singular
• case: nominative

The basic masculine nominative singular ending for many adjectives is -ый (or sometimes -ой / -ий):

• бесплатн-ый – free (of charge)
• интересн-ый – interesting

Because урок is masculine, singular, nominative:

• бесплатный урок
• интересный урок
• Этот бесплатный урок интересный.

All the adjectives linked to урок in this sentence must share these features, so they all use the same masculine-nominative-singular form.

In this sentence, Russian is doing two different jobs with adjectives:

1. Attributive adjective (part of the noun phrase):

   • Этот бесплатный урок – this free lesson
     Here бесплатный is simply describing what kind of lesson it is.

2. Predicative adjective (part of the “is …” part of the sentence):

   • урок интересный – the lesson is interesting

Combine them:

• Этот бесплатный урок интересный.
  literally: This free lesson (is) interesting.

So интересный is at the end because it functions like the predicate (“is interesting”), not just a simple modifier.

Contrast:

• интересный урок – an interesting lesson (single noun phrase)
• урок интересный – the lesson is interesting (full sentence)

Yes, you can say:

• Этот бесплатный урок интересен.

Here интересен is the short form adjective. The original интересный is the long form.

Both are grammatically correct and mean essentially the same thing: This free lesson is interesting. The difference is mostly stylistic:

• Урок интересный.
  – very common, neutral, everyday style.
• Урок интересен.
  – a bit more concise, sometimes feels slightly more formal, bookish, or “evaluative”.

In speaking, many people will naturally use the long form (интересный) in this kind of sentence. The short form is still widely used, but you don’t have to use it here.

There are two common patterns:

1. Adjective agreeing with a noun

   • урок интересный – the lesson is interesting
     (интересный agrees with урок, which is masculine singular.)

2. Neuter predicative/adverbial form used in impersonal sentences:

   • Мне интересно. – It is interesting to me / I find it interesting.
   • Было интересно. – It was interesting.

In Этот бесплатный урок интересный, we have a clear subject (урок), so Russian prefers the adjective form that agrees with the noun:

• урок (masc. sg.) → интересный (masc. sg.)

Этот бесплатный урок интересно by itself is incorrect. You could say instead:

• Мне интересно на этом бесплатном уроке. – I find this free lesson interesting / It’s interesting for me in this free lesson.

Both can be translated as “free” in English, but they mean different kinds of “free”:

• бесплатный – free of charge, no payment

  • бесплатный урок – a lesson you don’t pay for
  • бесплатный кофе – free coffee (no cost)

• свободный – free, not occupied / not busy / free in status

  • свободное время – free time
  • свободное место – free seat / vacant place
  • Я свободен. – I’m free / I’m not busy.

So Этот бесплатный урок clearly means: This lesson costs nothing, not “this lesson is currently not occupied.”

In Этот бесплатный урок интересный, урок is the subject, so it is in the nominative case (именительный падеж).

Here is the full declension of урок (singular / plural):

• Nominative:
  
  • урок / уроки – a lesson / lessons
• Genitive:
  
  • урока / уроков – of a lesson / of lessons
• Dative:
  
  • уроку / урокам – to a lesson / to lessons
• Accusative:
  
  • урок / уроки – (do) a lesson / (do) lessons
• Instrumental:
  
  • уроком / уроками – with/by a lesson / with lessons
• Prepositional:
  
  • уроке / уроках – about/on a lesson / about lessons

Because in our sentence урок is just “lesson” as the subject, it stays in the basic nominative form.

Stresses (marked with ´):

• Э́тот беспла́тный уро́к интере́сный.

Stress pattern:

• Э́тот – stress on Э
• беспла́тный – stress on пла́т
• уро́к – stress on о́к
• интере́сный – stress on е́с

Approximate IPA transcription:

• [ˈetət bʲɪsˈplatnɨj ʊˈrok ɪntʲɪˈrʲesnɨj]

Try to keep one main stress per word and avoid stressing every syllable equally (English speakers often do that at first).

Yes, Russian word order is fairly flexible, but small changes can affect focus and naturalness.

Some common, natural options:

1. Этот бесплатный урок интересный.
   – neutral: This free lesson is interesting.

2. Этот урок бесплатный и интересный.
   – This lesson is free and interesting.
   Both adjectives are clearly predicates (part of “is …”).

3. Этот интересный урок бесплатный.
   – This interesting lesson is free.
   Now the focus is more on “it is free”, since интересный comes earlier as an attributive description.

4. Интересный бесплатный урок.
   – no verb; just a noun phrase: an interesting free lesson.
   This is not a complete sentence; it’s like a title or a phrase, not “The lesson is interesting.”

What sounds odd as a full sentence:

• Этот бесплатный интересный урок.
  – This sounds like just a long noun phrase (this free interesting lesson), and the listener may wait for a verb. As a standalone sentence, it’s incomplete.

For a full sentence with the meaning “is interesting”, you need either a predicative adjective at the end (интересный / интересен) or some explicit verb form.