Wieczorem mówimy o jutrzejszym planie.

Both are related to evening, but they have different grammatical forms and functions:

• wieczór is the basic noun (nominative singular): evening.

  • e.g. Ten wieczór jest spokojny. – This evening is calm.

• wieczorem is the instrumental form, and in this context it works like an adverb of time, meaning in the evening / at night (in the evening time).

  • e.g. Wieczorem mówimy… – In the evening we talk…

Polish very often uses the instrumental case of time nouns in this adverb-like way:

• rano / rankiem – in the morning
• popołudniem – in the afternoon
• nocą – at night

So Wieczorem mówimy… is more natural than Wieczór mówimy…, which would be ungrammatical here.

Yes. Polish word order is quite flexible.

All of these are grammatically correct:

• Wieczorem mówimy o jutrzejszym planie.
• Mówimy wieczorem o jutrzejszym planie.
• O jutrzejszym planie mówimy wieczorem.

The neutral, most typical word order in this sentence is the original one, but changing the order can add emphasis:

• Starting with Wieczorem emphasizes when we talk.
• Starting with O jutrzejszym planie emphasizes what we talk about.
• Starting with Mówimy is a bit more neutral/statement-like: We talk (and the details follow).

mówimy is:

• 1st person plural: we
• Present tense
• From the verb mówić – to speak, to talk, to say

So literally mówimy = we talk / we are talking.

However, Polish present tense can also refer to the near future, especially when it’s about plans or schedules:

• Jutro o 10 mówimy o projekcie. – Tomorrow at 10 we are talking about the project.

In your sentence:

• Wieczorem mówimy o jutrzejszym planie.
  can mean:
  • In the evenings we talk about tomorrow’s plan. (habitual)
  • This evening we’re talking about tomorrow’s plan. (arranged future, depending on context)

In this meaning (about something), o always takes the locative case.

• o
  • locative: o kim? o czym? – about whom? about what?

In the sentence:

• o jutrzejszym planie
  • jutrzejszym – locative singular masculine (from jutrzejszy – tomorrow’s)
  • planie – locative singular masculine (from plan – plan)

So both words are in the locative to agree with o.

Compare:

• Mówimy o filmie. – We are talking about the film.
• Mówimy o pracy. – We are talking about work.

jutro is an adverb meaning tomorrow. You can’t put it directly after o, because o needs a noun in the locative case, not an adverb.

So:

• Incorrect: o jutro plan
• Correct idea: use a noun phrase that means the plan for tomorrow:
  • o jutrzejszym planie – about tomorrow’s plan (literally: about the tomorrow-ish plan)
  • or: o planie na jutro – about the plan for tomorrow

jutrzejszy is an adjective derived from jutro and can be declined:

• jutrzejszy plan (nominative)
• o jutrzejszym planie (locative, after o)

Both mean plan for tomorrow, but the structure is slightly different:

• jutrzejszy plan / o jutrzejszym planie

  • Adjective-based: jutrzejszy (tomorrow’s).
  • Sounds very natural and a bit more compact.
  • Literally: tomorrow’s plan.

• plan na jutro / o planie na jutro

  • Prepositional phrase with na (for).
  • Also very common and totally correct.
  • Literally: plan for tomorrow.

In your sentence you could say:

• Wieczorem mówimy o jutrzejszym planie.
• Wieczorem mówimy o planie na jutro.

Both sound natural, with only a slight stylistic difference.

Polish does not have articles (a/an/the). The definiteness or indefiniteness is understood from context, not from a separate word.

So plan can mean:

• a plan
• the plan
• our plan depending on the situation and what both speakers know.

Wieczorem mówimy o jutrzejszym planie. could translate as:

• In the evening we talk about *the plan for tomorrow.*
• In the evening we talk about *our plan for tomorrow.* English has to choose an article; Polish does not.

jutrzejszym is the locative singular masculine form of the adjective jutrzejszy (tomorrow’s).

Pattern:

• Base adjective: jutrzejszy – tomorrow’s
• Masculine singular nominative: jutrzejszy plan – tomorrow’s plan
• Masculine singular locative: o jutrzejszym planie

The -ym ending is typical for masculine/neuter adjectives in the locative (and also instrumental) singular:

• nowy plan → o nowym planie
• ważny temat → o ważnym temacie
• jutrzejszy plan → o jutrzejszym planie

By itself, Wieczorem could mean:

• habitual: In the evenings / In the evening (generally, as a routine)
• one specific: This evening or tonight

The exact meaning depends on context and sometimes intonation:

• With additional adverbs like zwykle, zawsze, często it’s clearly habitual:

  • Wieczorem zawsze mówimy o jutrzejszym planie. – In the evenings we always talk about tomorrow’s plan.

• In a context of making plans for today, it’ll sound like this evening:

  • Rano idziemy na zakupy, a wieczorem mówimy o jutrzejszym planie.
    – In the morning we go shopping, and in the evening we talk about tomorrow’s plan.

Both can often be translated as we talk about the plan, but there’s a nuance:

• mówić o czymś – to say/talk/speak about something
  Focus is more on the act of saying or discussing content.

• rozmawiać o czymś – to converse, to have a discussion about something
  Emphasizes two-way conversation, interaction between people.

In your sentence, both are fine:

• Wieczorem mówimy o jutrzejszym planie.
• Wieczorem rozmawiamy o jutrzejszym planie.

The second one highlights more clearly that it’s a conversation between people, not, for example, one person giving a monologue.

For this sentence specifically:

• mówimy – the ó is pronounced like u:

  • mówimy ≈ muwimy (IPA: /muˈvʲimɨ/)

• wieczorem – there is e, not ą, but for reference:

  • nasal ą usually sounds like [ɔ̃] or [ɔw̃]/[on] depending on context.

• jutrzejszym:

  • j is like English y in yes.
  • rz is usually like the French j in jouer or the s in English measure (IPA: /ʐ/).
  • Roughly: yoo-tzheh-shym (more precisely: /juˈtʐɛjʂɨm/).

So the whole sentence, roughly:

• Wieczorem mówimy o jutrzejszym planie. ≈ Vyeh-CHO-rehm MOO-vee-mih oh yoo-TRZHEH-shym PLAH-nyeh.