Learn Hardcore Finnish: Minua väsyttää aamulla, joten juon kahvia. - I feel tired in the morning, so I drink coffee.

Minä olen väsynyt. = I am tired (describing your state, with minä as normal subject).
Minua väsyttää. = I feel tired / sleepiness is affecting me (experience hitting you from outside).

This pattern is very common with verbs like:

Minua paleltaa. = I feel cold.
Minua janottaa. = I am (feel) thirsty.
Minua naurattaa. = I feel like laughing / something makes me laugh.

What does väsyttää literally mean, and why is it in that form?

Väsyttää is a verb that roughly means “to tire, to make (someone) tired.”

In Minua väsyttää:

väsyttää is 3rd person singular (same form as hän väsyttää).
There is no explicit grammatical subject like “it” in English, but you can think of it as:
- “It makes me tired.” → Minua väsyttää.

So the structure is:

[Experiencer in partitive] + väsyttää (3rd person)
Minua väsyttää. = I feel tired / It makes me tired.

Why don’t we say “minä väsyttän” or something similar?

The verb väsyttää doesn’t work like a normal “I do X” verb in this meaning. The pattern is:

Minua väsyttää. (literally “It tires me”)
Not Minä väsyttän, which would be more like “I tire (someone)” and is not used in this sense.

With verbs for feelings/physical states, Finnish often uses an impersonal construction:

Minua väsyttää. = I feel tired.
Minua särkee. = I have pain / something aches.
Minua oksettaa. = I feel nauseous.

So the verb stays in 3rd person singular, and the experiencer is partitive (minua, sinua, häntä, etc.).

Can I say “Olen väsynyt aamulla” instead of “Minua väsyttää aamulla”? What’s the difference?

Both are correct, but the nuance is a bit different:

Olen väsynyt aamulla.
- I am tired in the morning.
- Describes your state more statically (like a characteristic or general condition).
Minua väsyttää aamulla.
- I feel tired in the morning / I get sleepy in the morning.
- Emphasizes the feeling as something affecting you, often a bit more immediate or experiential.

In everyday speech, Minua väsyttää is very common when talking about how you feel at a given time.

Why is it aamulla instead of just aamu? What does that ending mean?

Aamulla is the adessive case of aamu (morning).

aamu = morning (basic form)
aamulla = in the morning (literally “at/on morning”)

So Minua väsyttää aamulla = I feel tired in the morning.

Compare:

yöllä = at night (from yö, night)
illalla = in the evening (from ilta, evening)
päivällä = in the daytime (from päivä, day)

Could I use aamuisin instead of aamulla? What’s the difference?

Yes, you can:

Minua väsyttää aamulla.
- I feel tired in the morning (this morning, or mornings in general, depending on context).
Minua väsyttää aamuisin.
- I feel tired in the mornings (as a habit, regularly).

Aamuisin has a stronger sense of habitual / regularly on mornings, while aamulla can be either specific or general, depending on context.

What does joten mean, and how is it different from koska or siksi?

Joten is a conjunction meaning “so, therefore”.

In the sentence:

Minua väsyttää aamulla, joten juon kahvia.
→ I feel tired in the morning, so I drink coffee.

Rough comparison:

koska = because (introduces the reason)
- Juon kahvia, koska minua väsyttää aamulla.
  = I drink coffee because I feel tired in the morning.
joten = so, therefore (introduces the result)
- Minua väsyttää aamulla, joten juon kahvia.
  = I feel tired in the morning, so I drink coffee.
siksi = for that reason, that’s why (an adverb)
- Minua väsyttää aamulla, siksi juon kahvia.
  = I feel tired in the morning, that’s why I drink coffee.

All are correct; they just connect the clauses in slightly different logical ways.

Why is it kahvia and not kahvi in juon kahvia?

Kahvia is the partitive form of kahvi (coffee).

With verbs like juoda (to drink), when you drink an unspecified amount of a liquid or other mass noun, Finnish uses the partitive:

Juon kahvia. = I drink (some) coffee.
Juon vettä. = I drink (some) water.
Syön leipää. = I eat (some) bread.

If you use kahvi in a different case like kahvin (genitive), it usually refers to a specific, whole unit, often “one coffee” (e.g. one cup you ordered):

Juon kahvin. = I drink the (one) coffee / I’ll finish this coffee.

So juon kahvia is the natural way to say “I drink coffee” in a general or habitual sense.

Can the word order change? For example, can I say “Aamulla minua väsyttää, joten juon kahvia”?

Yes, Finnish word order is fairly flexible, especially for information structure (what you want to emphasize).

All of these are grammatical:

Minua väsyttää aamulla, joten juon kahvia.
Aamulla minua väsyttää, joten juon kahvia. (emphasis on in the morning)
Minua aamulla väsyttää, joten juon kahvia. (emphasis on me, in the morning)

The choice mainly affects emphasis and rhythm, not basic meaning. The original sentence is the most neutral.

Why is it just juon kahvia and not minä juon kahvia? Where did the subject go?

The subject minä is simply left out, because Finnish normally omits personal pronouns when the person is clear from the verb ending.

juon = I drink (1st person singular)
minä juon is correct but usually only used for emphasis or clarity.

In the first clause we see minua, so we already know the person is I. In the second clause, juon clearly marks 1st person singular, so minä isn’t necessary:

Minua väsyttää aamulla, joten juon kahvia.
= I feel tired in the morning, so I drink coffee.