Сегодня я задержусь в офисе, поэтому не смогу прийти на семинар.

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Questions & Answers about Сегодня я задержусь в офисе, поэтому не смогу прийти на семинар.

Why is задержусь in the future tense if the sentence starts with Сегодня (today)?
In Russian, Сегодня can refer to any time within today, including later. Я задержусь is future: it means you will stay late (later today). Russian often uses the simple future to describe something that will happen later the same day.
What does задержусь come from, and what does it literally mean?
Задержусь is the 1st person singular future form of the perfective verb задержаться (to be delayed / to stay longer than planned). Literally it’s like I will end up staying / I will run late (here: at the office).
Why is it задержусь, not задерживаюсь?

Задерживаюсь is present tense (imperfective) and usually means a current situation or a repeated habit:

  • Я задерживаюсь = I’m staying late (right now) / I tend to stay late (often). Я задержусь (perfective future) points to a single, specific instance in the future: today I will stay late.
What’s the difference between -ся and -сь in задержусь?

They’re the same reflexive ending; -сь is just a shortened form used after vowels for easier pronunciation:

  • задержу + сь → задержусь Compare:
  • задержался (ends in a consonant, so -ся)
  • задержусь (ends in a vowel, so -сь)
Why is it в офисе and not в офис?

Because this is location, not direction.

  • в офисе = in the office (Prepositional case, location)
  • в офис = into the office (Accusative case, motion toward a place)
Why is there a comma before поэтому?

Because поэтому here links two clauses with a cause–result relationship:

  • Сегодня я задержусь в офисе, поэтому не смогу... A comma is standard when поэтому functions like so/therefore connecting clauses.
What’s the difference between поэтому and потому что?

They express the relationship from different sides:

  • потому что = because (gives the reason): Я не смогу прийти, потому что задержусь.
  • поэтому = therefore/so (gives the result): Я задержусь, поэтому не смогу прийти. Both are correct; they just structure the sentence differently.
Why is it не смогу, not не могу?

не смогу is future: I won’t be able to (later). не могу is present: I can’t (right now, at the moment). Since the speaker is talking about later today (because they will stay late), не смогу fits.

What verb is смогу and what tense/aspect is it?
смогу is the 1st person singular simple future of the perfective verb смочь (to be able, to manage). Perfective here expresses a single future ability/possibility (or lack of it): I won’t be able to (make it).
Why is it прийти (perfective) and not приходить?

With смочь / не смочь, Russian commonly uses the infinitive that matches a single completed event:

  • прийти = to come (once, to arrive)
  • приходить = to come (habitually or process) Here it’s about one specific arrival at one seminar, so прийти is natural.
Why is it прийти на семинар (with на) and not в семинар?

Events in Russian usually take на:

  • на семинар, на лекцию, на встречу, на концерт в is used more for enclosed places/venues as locations (в офисе, в школе, в театре—though even with venues, events are still often на: на спектакль).
Can I change the word order, or is this fixed?

It’s flexible, but some orders sound more neutral:

  • Neutral: Сегодня я задержусь в офисе, поэтому не смогу прийти на семинар. You can shift сегодня or в офисе for emphasis:
  • Я сегодня задержусь в офисе... (emphasizes today vs other days)
  • В офисе я сегодня задержусь... (emphasizes the office)
Is я necessary here, or can it be dropped?

It can be dropped because the verb ending already shows the subject:

  • Сегодня задержусь в офисе, поэтому не смогу прийти на семинар. Including я is still common and can add clarity or emphasis, especially in longer contexts.