Seuranta alkaa seuraavan tapaamisen jälkeen.

Because jälkeen is a postposition that requires the noun phrase before it to be in the genitive.

So:

• seuraava tapaaminen = the next meeting/appointment in the basic form
• seuraavan tapaamisen jälkeen = after the next meeting/appointment

This is a very common Finnish pattern:

• ruoan jälkeen = after the food / after eating
• kokouksen jälkeen = after the meeting
• työn jälkeen = after work

So the important rule is:

genitive noun phrase + jälkeen = after something

Jälkeen means after, but unlike English after, it comes after the word it belongs to. That makes it a postposition rather than a preposition.

English:

• after the meeting

Finnish:

• tapaamisen jälkeen

So in Finnish, many words that express relations like after, before, without, in front of, and so on may come after the noun phrase instead of before it.

That is why the sentence is structured this way:

• seuraavan tapaamisen jälkeen = after the next appointment

Tapaaminen is a -minen noun, made from a verb. These nouns have a special pattern when they are inflected.

Basic form:

• tapaaminen

Genitive:

• tapaamisen

What happens is that the stem changes from -minen to -mise- before case endings:

• tapaaminen → tapaamise-
  • n → tapaamisen

This same pattern happens with many other -minen nouns:

• lukeminen → lukemisen
• syöminen → syömisen
• opiskeleminen → opiskelemisen

So this is not random: it is a normal inflection pattern for -minen nouns.

It is a noun here.

It comes from the verb tavata, which means to meet, but tapaaminen means meeting or appointment.

So although it is related to a verb, in this sentence it behaves just like a regular noun:

• it can take case endings
• it can be modified by an adjective
• it can be the object of a postposition

That is why you get:

• seuraava tapaaminen = next appointment
• seuraavan tapaamisen jälkeen = after the next appointment

Because alkaa means to begin / to start in an intransitive way: something begins.

Here, seuranta is the thing that begins:

• Seuranta alkaa = The follow-up begins

By contrast, aloittaa usually means to start something in a transitive way: someone starts something.

Compare:

• Seuranta alkaa. = The follow-up begins.
• Lääkäri aloittaa seurannan. = The doctor starts the follow-up.

So in this sentence, alkaa is the natural choice because the subject itself is beginning.

Seuranta is the subject of the sentence, and it is in the nominative singular basic form.

The sentence structure is:

• Seuranta = subject
• alkaa = verb
• seuraavan tapaamisen jälkeen = time expression using a postposition

So the core of the sentence is:

• Seuranta alkaa = Follow-up begins

Then the rest adds when it begins:

• seuraavan tapaamisen jälkeen = after the next appointment

Finnish does not have articles like English the and a/an.

So a noun like seuranta can mean:

• follow-up
• the follow-up

And tapaaminen can mean:

• a meeting
• the meeting
• an appointment
• the appointment

Which one is meant depends on the context.

In this sentence, English usually needs something like the follow-up and the next appointment, but Finnish does not mark that with separate article words.

Both seuraava and ensi can often be translated as next, but they are not always identical.

A useful rough distinction is:

• seuraava = the following one in a sequence
• ensi = the next upcoming one, often from the current moment

So seuraava tapaaminen suggests the following appointment/meeting in the sequence. That fits very naturally here.

In many everyday situations, ensi tapaaminen might also be possible, but seuraava is often a bit more neutral and sequence-based.

So:

• seuraavan tapaamisen jälkeen = after the following/next appointment

Yes. Tapaaminen can mean either meeting or appointment, depending on context.

For example:

• in business, it may mean meeting
• in medical or administrative contexts, it often means appointment

So if this sentence appears in a healthcare context, seuraavan tapaamisen jälkeen may be understood as:

• after the next appointment

If it appears in a general work context, it may mean:

• after the next meeting

The Finnish word itself allows both readings.

The given order is the most neutral one:

• Seuranta alkaa seuraavan tapaamisen jälkeen.

But Finnish word order is fairly flexible, so you could move the time phrase for emphasis:

• Seuraavan tapaamisen jälkeen seuranta alkaa.

That version puts more focus on when it begins.

Both are grammatical. The original sentence is just the most straightforward, neutral way to say it.

No, here seuranta does not mean literally walking behind someone.

It comes from the verb seurata, which can mean to follow, but the noun seuranta usually means something like:

• monitoring
• follow-up
• observation
• tracking

In medical, administrative, or technical contexts, seuranta very often means an ongoing follow-up or monitoring process.

So in this sentence, it refers to that kind of organized follow-up, not physical movement.