Menemme postiin ostamaan kirjekuoria ja lähettämään kirjeen.

We go to the post office to buy envelopes and send a letter.

Breakdown of Menemme postiin ostamaan kirjekuoria ja lähettämään kirjeen.

• ja: and
• mennä: to go
• ostaa: to buy
• -in: to
• lähettää: to send
• kirje: the letter
• posti: the post office
• kirjekuori: the envelope

Questions & Answers about Menemme postiin ostamaan kirjekuoria ja lähettämään kirjeen.

Why is it postiin and not posti, postissa, or postille?

Postiin is the illative case, which often corresponds to English “to (a place)” or “into (a place)”.

• posti = the post / mail, or post office (basic form)
• postissa (inessive) = in/at the post office
  • Olen postissa. = I am at the post office.
• postiin (illative) = to the post office
  • Menemme postiin. = We are going to the post office.
• postille (allative) = to the post(-office) but with the idea of “onto / to the surface / to the use of”. You would more often see this with services, e.g. lähetän sen postille can mean I send it via the post (to the postal service).

With verbs of movement like mennä (to go), tulla (to come), juosta (to run), Finnish usually uses the illative for “going to a place”:

• Menen kouluun. = I go to school.
• Tulen kauppaan. = I’m coming to the shop.
• Menemme postiin. = We are going to the post office.

So postiin is exactly the normal “to the post office” form here.

What are ostamaan and lähettämään? Why don’t we just use ostaa and lähettää?

Ostamaan and lähettämään are not ordinary present-tense verbs. They are the third infinitive in the illative case (often called the -maan/-mään form).

They are used very frequently to express purpose, especially after verbs of motion:

• mennä ostamaan = to go (in order) to buy
• mennä lähettämään = to go (in order) to send

Structure in this sentence:

• Menemme = we go / we are going
• postiin = to the post office
• ostamaan = to (for) buying
• lähettämään = to (for) sending

So the sentence literally has the structure:

We go to the post office *for buying envelopes and for sending a letter.*

Using the basic infinitive ostaa, lähettää here would be ungrammatical:

• ❌ Menemme postiin ostaa kirjekuoria ja lähettää kirjeen.

You need the -maan/-mään form to show this “go in order to do X” meaning.

Why does one verb take -maan and the other -mään: ostamaan vs lähettämään?

The difference is due to vowel harmony in Finnish.

• ostaa → ostama- → ostamaan
  • The stem has back vowels (o, a). With back vowels, the ending is -maan.
• lähettää → lähettä- → lähettämään
  • The stem has front vowels (ä, e). With front vowels, the ending is -mään.

Rule of thumb:

• If the word has only back vowels (a, o, u), you get -maan.
• If it has any front vowels (ä, ö, y) and no back vowels, you get -mään.

So:

• ostaa → ostamaan
• auttaa → auttamaan
• opiskella → opiskelemaan
• lähettää → lähettämään
• pestä → pesemään

Why do we repeat the -maan/-mään form: ostamaan kirjekuoria ja lähettämään kirjeen? Could it be just ostamaan kirjekuoria ja lähettää kirjeen?

You must repeat the same verbal form for both verbs in this construction.

Here, mennä governs an -maan/-mään infinitive expressing purpose. When you coordinate two activities with ja (and), they both have to appear in the same form:

• ✅ Menemme postiin ostamaan kirjekuoria ja lähettämään kirjeen.
• ❌ Menemme postiin ostamaan kirjekuoria ja lähettää kirjeen.

The ungrammatical version mixes two different forms:

• ostamaan (3rd infinitive illative)
• lähettää (basic infinitive)

Both verbs here are equally dependent on menemme postiin (“we go to the post office [in order] to ...”), so they both must appear as ostamaan / lähettämään.

Why is kirjekuoria in the partitive plural, but kirjeen is in the genitive singular?

This is about object case, which in Finnish also encodes things like quantity and completeness.

1. kirjekuoria (partitive plural of kirjekuori = envelope)

   • Form: kirjekuori → kirjekuoria
   • Used when buying an unspecified amount or some envelopes.
   • With verbs like ostaa (to buy), the partitive is often used when the quantity is:
     • not exact
     • not known in advance
   • So: ostamaan kirjekuoria = to buy (some) envelopes.

2. kirjeen (genitive singular of kirje = letter)

   • Form: kirje → kirjeen
   • This is the total object case (often genitive singular) showing a complete, bounded action on one whole item.
   • lähettää kirjeen implies sending that one whole letter, and the action is expected to be completed.

Compare:

• Lähetän kirjettä. (partitive)
  = I am sending a letter / I’m in the process, not necessarily finished.
• Lähetän kirjeen. (genitive total object)
  = I (will) send the letter completely, get it sent.

In the original sentence:

• kirjekuoria = some number of envelopes (unspecified)
• kirjeen = one specific complete letter.

Could we say ostamaan kirjekuoret instead of ostamaan kirjekuoria? How would that change the meaning?

Yes, you could say ostamaan kirjekuoret, but the nuance changes.

• ostamaan kirjekuoria (partitive plural)

  • to buy (some) envelopes, unspecified quantity.
  • Typical when you just mean “we’ll buy envelopes”, no fixed set in mind.

• ostamaan kirjekuoret (nominative/“total” plural)

  • Implies a specific, known set of envelopes.
  • For example, the particular envelopes we already talked about or planned to get:
    • We’re going to the post office to buy *the envelopes (that we need / that we mentioned).*

So:

• If you just need some envelopes, kirjekuoria is more natural.
• If you and the listener know exactly which envelopes (a definite set), kirjekuoret fits.

Why is it lähettämään kirjeen and not lähettämään kirjettä?

Again, this is the object case: kirjeen (genitive) vs kirjettä (partitive).

• lähettämään kirjeen

  • Genitive kirjeen = total object.
  • The action is directed at one whole letter and is expected to be completed.
  • Meaning: go to send the letter (and get it sent).

• lähettämään kirjettä

  • Partitive kirjettä = incomplete / ongoing / unbounded action.
  • Would suggest going to be in the process of sending a letter, which is unusual in this concrete context.
  • It sounds off unless you have some very specific context (e.g. a long, ongoing, somehow incomplete “sending” process).

For simple, concrete tasks like mailing a letter, Finnish prefers the total object kirjeen.

Could the word order be different, e.g. Postiin menemme ostamaan kirjekuoria ja lähettämään kirjeen?

Yes, Finnish word order is relatively flexible. All of these are grammatical:

• Menemme postiin ostamaan kirjekuoria ja lähettämään kirjeen.
  (neutral, typical)
• Postiin menemme ostamaan kirjekuoria ja lähettämään kirjeen.
• Menemme ostamaan kirjekuoria ja lähettämään kirjeen postiin.
  (still usually interpreted as “to the post office”, though a bit less natural)

What changes is mainly emphasis and information structure, not the core meaning.

• Putting Postiin first (Postiin menemme...) puts focus on where you are going, maybe in contrast to some other place:

  • We’re going *to the post office to buy envelopes...* (not somewhere else).

• Keeping Menemme postiin ... is the most neutral and common order in everyday speech.

Note: If you put postiin after kirjeen, some contexts might let it be read as “to the post” in a more abstract sense, but here people will almost always understand it as “to the post office” because the verb is menemme (we go).

Why is menemme translated as “we are going” and not just “we go”? What tense is it?

Menemme is Finnish present tense, 1st person plural:

• mennä (to go) → menemme (we go / we are going)

Finnish has only one present tense form, and it covers both:

• English simple present: we go
• English present continuous: we are going

The exact English translation depends on context:

• Menemme postiin joka päivä.
  → We go to the post office every day. (habit → simple present)

• Menemme postiin ostamaan kirjekuoria...
  → We are going to the post office to buy envelopes...
  (a situation happening now or in the near future → present continuous)

So the Finnish form menemme itself does not distinguish these; English has to choose one based on context.

Is menemme what people really say in everyday speech, or is there a more colloquial form?

In standard Finnish, menemme is the correct 1st person plural form: we go / we are going.

In spoken colloquial Finnish, people very often use the so‑called “passive” form with me, for example:

• Me mennään postiin ostamaan kirjekuoria ja lähettämään kirje.

Differences:

• Standard:
  
  • Menemme postiin ostamaan...
• Colloquial:
  
  • Me mennään postiin ostamaan...

Both mean the same thing. Menemme sounds more formal / written; me mennään is what you’ll hear very often in everyday conversation.

Does posti here mean “mail” or specifically “post office”? How do I know?

Posti can mean several related things:

1. the mail / postal system
   • Sain postia. = I got mail.
2. the postal service (organization)
   
   • Posti = the Finnish postal company.
3. a post office
   • Menemme postiin. = We’re going to the post office.

In your sentence, the meaning “post office” is clear from:

• The case: postiin (illative, going to a place)
• The activities: ostamaan kirjekuoria ja lähettämään kirjeen are things you do at a post office.

So context + case ending tell you that posti here is understood as the post office.