Learn Hardcore Russian: Мы обсуждаем приставку «по-» на уроке. - We are discussing the prefix "по-" in the lesson.

Обсуждаем is the 1st person plural, present tense, imperfective form of the verb обсуждать (to discuss).
It literally means “we discuss / we are discussing.”

Person/number: мы обсуждаем = we discuss
Tense: present
Aspect: imperfective (focus on the process or repeated action, not on the result)

So this form tells us who is acting (we), when (now, in general or at this time), and that the focus is on the ongoing/repeated action, not on completion.

Why is it приставку, not приставка, in this sentence?

Приставку is in the accusative case, singular, feminine.

The noun’s base form (nominative) is приставка (a prefix), but обсуждать кого? что? takes a direct object in the accusative.
Feminine nouns ending in -a in the nominative usually change -a → -у in the accusative singular:

приставка → приставку
книга → книгу
комната → комнату

So обсуждаем приставку means “(we) discuss the prefix.”

Why don’t we say обсуждаем о приставке по-? In English we say “discuss about…”

In Russian, обсуждать is a transitive verb and takes a direct object without a preposition:

обсуждать план – to discuss a plan
обсуждать проблему – to discuss a problem
обсуждать приставку по- – to discuss the prefix по-

Saying обсуждать о чем‑то is wrong; you only use о + prepositional with verbs like говорить о, думать о, рассказывать о:

говорить о приставке по- – to talk about the prefix по-

So the correct form here is обсуждаем приставку по-, not обсуждаем о приставке по-.

Why do we use на уроке instead of в уроке? What case is уроке?

Уроке is in the prepositional case, singular, masculine, after the preposition на.

With lessons, lectures, classes, and events, Russian normally uses на + prepositional to mean “in/at (an event)”:

на уроке – in/at the lesson
на лекции – at the lecture
на встрече – at the meeting

Saying в уроке is not used in this meaning. So на уроке is an idiomatic, standard phrase meaning “during the lesson / in class.”

Can we leave out мы and just say Обсуждаем приставку по- на уроке?

Yes, that is grammatically possible.

Russian verb endings already show the person and number, so the subject pronoun is often dropped when it’s clear from context:

Обсуждаем приставку по- на уроке. – We’re discussing the prefix по- in class.

Including мы can add slight emphasis to “we (and not someone else)”, or just sound a bit more explicit or neutral, depending on context. Both versions are correct.

Can we change the word order, for example: Приставку по- мы обсуждаем на уроке or Мы на уроке обсуждаем приставку по-?

Yes. Russian word order is flexible, and all these are correct, but the emphasis changes slightly:

Мы обсуждаем приставку по- на уроке. – neutral, simple statement.
Мы на уроке обсуждаем приставку по-. – slight emphasis on “in class we discuss the prefix по-” (what we do in class).
Приставку по- мы обсуждаем на уроке. – emphasis on “It’s the prefix по- that we discuss in class” (contrast with other topics).

Grammatically they all mean the same thing; the difference is what part you highlight.

Why is the verb in the present tense обсуждаем, even though in English we might say “are discussing”? Does Russian have a separate continuous tense?

Russian has only one present tense form for both “we discuss” and “we are discussing.”

Мы обсуждаем can mean:

“We discuss (in general / regularly)”
“We are discussing (right now)”

Context tells you whether it’s a general habit or something happening at the moment. There is no separate continuous/progressive tense in Russian like am/is/are + -ing in English.

Why is обсуждаем imperfective? How would the sentence change with the perfective verb обсудить?

Обсуждаем is from the imperfective verb обсуждать. Imperfective aspect is used for:

Ongoing actions (what we are doing now)
Repeated/regular actions
Processes without focusing on completion

If you change it to the perfective:

Мы обсудим приставку по- на уроке. – We will discuss the prefix по- in the lesson (single, completed action in the future).
Мы обсудили приставку по- на уроке. – We discussed the prefix по- in the lesson (completed action in the past).

Perfective present forms like обсудим normally refer to the future, not the present.

Why is the prefix written as по- with a hyphen?

When talking about a prefix as a grammatical unit, Russian normally writes it with a hyphen to show that it attaches to a word:

приставка по- – the prefix po-
приставка вы- – the prefix vy-
суффикс -ка – the suffix -ка

The hyphen signals that по- is not a separate independent word but something that joins to another word (e.g. поехать, почитать). So in grammar explanations you’ll usually see prefixes written with a hyphen.

How do you pronounce the stressed syllables in обсуждаем приставку по- на уроке?

Stresses:

обсуждАем – stress on -да-: ob-su-ždÁ-em
пристАвку – stress on -та-: pri-stÁv-ku
пО- (when named as an item) – stress on по
урОке – stress on -ро-: u-rÓ-ke

Phonetically (rough guide):
мы обсуждаем приставку по- на уроке → my obsuzhdÁyem prístavku pó na urÓke.

In English we say “the prefix по-”. Why is there no word for “the” or “a” in приставку по-?

Russian has no articles (no “a/an” or “the”).

Nouns like приставка / приставку by themselves can mean “a prefix” or “the prefix” depending on context and what is already known in the conversation.
Here, because both speaker and listener know which prefix is meant (по-), English uses “the prefix по-”, but Russian just uses приставку по- with no article.

What is the difference between обсуждать приставку по- and говорить о приставке по-?

Both can be translated as “talk about / discuss,” but the nuance is different:

обсуждать приставку по- – to discuss the prefix по-, often implying a more focused, analytical, or systematic discussion (e.g. its meanings, uses, rules).
говорить о приставке по- – to talk about the prefix по- more generally; it can be less formal, not necessarily analyzing it in detail.

In your sentence, обсуждаем приставку по- suggests a more deliberate, “lesson-style” discussion, which fits the classroom context на уроке.