Мои будние дни отличаются от выходных.

My weekdays are different from my weekends.

Breakdown of Мои будние дни отличаются от выходных.

• мой: my
• от: from
• выходные: the weekend
• будний день: the weekday
• отличаться: to be different

Questions & Answers about Мои будние дни отличаются от выходных.

Why is it мои будние дни and not мой будний день?

Because the speaker is talking about their weekdays in general, not about a single weekday.

• день = day (singular)
• дни = days (plural)

So:

• мой будний день = my weekday (one day)
• мои будние дни = my weekdays (all of them, as a group)

The rest of the sentence (verb and everything else) is also in the plural, so you need the plural subject мои будние дни.

What exactly does будние дни mean, and how is it different from будни?

Both refer to weekdays / working days, but there is a small nuance:

• будние дни – literally weekday days, a neutral, clear phrase for “weekdays” (Monday–Friday, or working days).
• будни – more like “the workweek / everyday routine / weekday life,” slightly more abstract or “the grind of everyday life.”

In most everyday contexts, будни and будние дни can be used interchangeably, and you could also say:

• Мои будни отличаются от выходных. – stylistically a bit shorter and very natural.

Why is the verb отличаются and not something like есть разные?

Russian normally expresses “X is different from Y” with the verb отличаться (от чего?) rather than with a form of “to be different” + an adjective:

• Мои будние дни отличаются от выходных.
  = My weekdays are different from my weekends.

Using есть разные here (“мои будние дни есть разные от выходных”) would be unnatural or wrong. The standard pattern is:

• X отличается от Y – X differs from Y / X is different from Y

What does the -ся ending in отличаются mean?

The -ся makes the verb reflexive, turning отличать into отличаться:

• отличать (что‑то от чего‑то) – to distinguish something from something
  
  • Я отличаю одно от другого. – I distinguish one from the other.
• отличаться (от чего‑то) – to differ from something / to be different from something
  
  • Мои будние дни отличаются от выходных. – My weekdays differ from my weekends.

So отличаются here is 3rd person plural, present tense, reflexive: “(they) differ.”

What case is выходных in, and why is it used?

выходных is genitive plural.

The verb отличаться takes the preposition от, and от always requires the genitive case:

• отличаться от кого? чего?

So we have:

• выходные (дни) – nominative plural (weekends / days off)
• от выходных (дней) – genitive plural (from weekends)

That’s why the form changes to выходных.

Why is it just от выходных and not от выходных дней?

The word выходные already commonly means weekends or days off, so the noun дни is often omitted:

• выходные дни – literally days off (days)
• выходные – usual everyday way to say weekends / days off

In genitive plural, both would be:

• от выходных дней – more explicit, but a bit heavier
• от выходных – shorter, fully natural, and what people usually say

In your sentence, от выходных is perfectly standard and idiomatic.

Could I say Мои будние дни разные от выходных instead?

That sounds unnatural in Russian. To express “different from,” Russian uses:

• различаться / отличаться от чего‑то (verbs),
  not разный от (adjective + от).

Correct natural options:

• Мои будние дни отличаются от выходных.
• Мои будние дни сильно отличаются от выходных.
• Мои будние дни и выходные сильно различаются.

But *будние дни разные от выходных is not idiomatic.

Can I change the word order, for example: От выходных отличаются мои будние дни?

Yes, Russian word order is flexible. These versions are all grammatically correct:

• Мои будние дни отличаются от выходных.
• От выходных отличаются мои будние дни.
• От выходных мои будние дни отличаются.

The basic / most neutral one is the original sentence. Moving parts around usually adds emphasis:

• От выходных отличаются мои будние дни. – emphasizes “From the weekends, it’s my weekdays that are different (not something else).”

What is the grammatical form of отличаются exactly?

отличаются is:

• from the verb отличаться (imperfective, reflexive)
• 3rd person plural
• present tense

So it means: “(they) differ / are different.”

Subject: мои будние дни (they) → verb: отличаются (they differ).

Is there any difference between будние дни and рабочие дни?

Yes, small nuance:

• будние дни – “weekdays,” usually understood as the days that are normally workdays (Mon–Fri), but doesn’t explicitly mention work.
• рабочие дни – “working days,” more directly tied to work / job / business schedule.

In most casual contexts about one’s routine, будние дни is slightly more neutral and common in a sentence like yours.

Both can contrast with выходные (дни) – weekends / days off.

How would I say “on weekdays” and “on weekends” using the same words?

Use the preposition по with dative plural:

• по будним дням – on weekdays
  
  • Я рано встаю по будним дням. – I get up early on weekdays.
• по выходным (дням) – on weekends
  
  • Я долго сплю по выходным. – I sleep in on weekends.

So your sentence talks about them in general (nominative plural), but with по you’d switch to dative plural: по будним дням, по выходным (дням).