Learn Hardcore Finnish: Erityisesti maanantaisin olen väsynyt, joten juon kahvia enemmän. - Especially on Mondays I am tired, so I drink more coffee.

maanantaina = on Monday (one specific Monday, or a single occasion)
- Esim. Maanantaina olen väsynyt. = On Monday I am tired (that particular Monday).
maanantaisin = on Mondays / every Monday / on Monday(s) in general
This -sin form expresses something that happens regularly or habitually.

So Erityisesti maanantaisin olen väsynyt = Especially on Mondays (as a rule, every Monday) I am tired.

What exactly is the -sin ending in maanantaisin?

The -sin ending turns certain nouns into adverbs of time that mean “regularly on X” or “on Xs” (habitually).

maanantai → maanantaisin = on Mondays
ilta (evening) → iltaisin = in the evenings
aamu (morning) → aamuisin = in the mornings
kesä (summer) → kesäisin = in the summers

So maanantaisin tells you not just when, but that it happens repeatedly at that time.

Why is there no minä in olen väsynyt?

Finnish usually drops personal pronouns like I, you, he/she because the verb ending already shows the person:

olen = I am
olet = you are
on = he/she/it is

So:

Olen väsynyt. = I am tired.
Minä olen väsynyt. = also correct, but usually used for emphasis (e.g. contrast: I am tired, not someone else).

In the sentence, Erityisesti maanantaisin olen väsynyt, it’s natural and normal not to use minä.

Why is there a comma before joten?

joten is a conjunction meaning roughly so / therefore. In writing, it usually starts a new clause, and Finnish typically puts a comma before it:

Olen väsynyt, joten juon kahvia enemmän.
= I’m tired, so I drink more coffee.

Other similar conjunctions that normally take a comma before them:

mutta = but
vaikka = although
koska = because
sillä = because / for

So the comma marks the boundary between the reason/result clause and the rest.

What’s the difference between joten, siksi, and koska here?

All relate to cause and effect, but they’re used differently:

joten = so / therefore (used between clauses)
- Olen väsynyt, joten juon kahvia enemmän.
  = I’m tired, so I drink more coffee.
siksi = for that reason / therefore (adverb; can move in the sentence)
- Olen väsynyt. Siksi juon kahvia enemmän.
  = I am tired. For that reason I drink more coffee.
koska = because (introduces a reason clause)
- Juon kahvia enemmän, koska olen väsynyt.
  = I drink more coffee because I’m tired.

So joten and siksi express the result, and koska introduces the cause.

Why is it juon kahvia (partitive) and not juon kahvin?

Kahvia is in the partitive case, which is used here for an indefinite amount of something, especially uncountable things like liquids:

juon kahvia = I drink coffee / I’m drinking (some) coffee
juon vettä = I drink water

Juon kahvin (accusative/genitive) is also correct but means something more like:

Juon kahvin. = I drink (up) the coffee / I finish the coffee.
→ a specific, delimited amount (often “that cup of coffee”).

In this sentence, we’re talking about how much coffee in general, so kahvia (partitive) is natural.

What’s the nuance difference between juon kahvia enemmän and juon enemmän kahvia?

Both mean I drink more coffee, but the focus shifts a bit:

juon kahvia enemmän
- Literally: I drink coffee more (than usual)
- Slight focus on the amount of drinking being higher.
juon enemmän kahvia
- Literally: I drink more coffee
- Slight focus on coffee as the thing of which there is more.

In everyday speech, both are fully natural; the difference is very subtle. Word order in Finnish often affects emphasis, not grammaticality.

Why is it enemmän, not something like enempi or enempiä?

Enemmän is the standard comparative adverb meaning more (in quantity):

paljon kahvia = a lot of coffee
enemmän kahvia = more coffee

Enempi is a dialectal / colloquial variant of enemmän in some regions, but enemmän is the form you should use in standard Finnish.

There is no plural or case ending attached to enemmän here because it works as an adverb modifying the verb phrase (juon kahvia).

Why is it erityisesti, not erityisen?

Erityisesti is an adverb (especially), ending in -sti, which is the common adverb ending:

erityinen = special (adjective)
erityisesti = especially (adverb)

Here we need to modify the whole situation (“on Mondays I am tired”), so we need an adverb:

Erityisesti maanantaisin olen väsynyt.
= Especially on Mondays I’m tired.

Erityisen is the genitive / instructive form of erityinen and is used before a noun:

erityisen hyvä kahvi = especially good coffee / particularly good coffee

So with a verb/clause, use erityisesti; with a noun, you might use erityisen + adjective + noun.

Why does the sentence start with Erityisesti maanantaisin instead of Olen erityisesti maanantaisin väsynyt?

Finnish has fairly flexible word order. Putting Erityisesti maanantaisin at the beginning:

Erityisesti maanantaisin olen väsynyt, joten juon kahvia enemmän.

does two things:

It highlights time (“especially on Mondays”) as the topic or emphasis.
It’s a very natural pattern: [Time / place] + verb + rest.

These versions are all grammatically correct, but differ slightly in emphasis:

Erityisesti maanantaisin olen väsynyt.
Olen erityisesti maanantaisin väsynyt.
Olen väsynyt erityisesti maanantaisin.

All can mean I am especially tired on Mondays. The chosen order just foregrounds the time expression.

Why is the verb in the present tense (olen, juon) even though it describes a habitual action?

In Finnish, the present tense is used both for:

actions happening right now
habitual or repeated actions (things you usually do)

So:

Juon kahvia.
→ could mean I’m drinking coffee (now) or I drink coffee (regularly).

In this sentence, the adverb maanantaisin (“on Mondays”) shows that it’s a habit, not a single moment. You don’t need a separate tense for that; present tense covers it.

Can I say Varsinkin maanantaisin olen väsynyt instead of Erityisesti maanantaisin olen väsynyt?

Yes. Both are natural, but there is a small nuance:

erityisesti = especially, particularly
varsinkin = especially, in particular

In many contexts, they are almost interchangeable:

Erityisesti maanantaisin olen väsynyt.
Varsinkin maanantaisin olen väsynyt.

For a learner, you can treat them as synonyms here. Erityisesti may sound a bit more neutral/formal; varsinkin is very common in speech.