Learn Hardcore Finnish: Varsinkin maanantaisin yritän mennä aikaisin nukkumaan, muuten olen koko päivän väsynyt. - Especially on Mondays I try to go to sleep early, otherwise I am tired the whole day.

Varsinkin maanantaisin at the start means: “As for Mondays, in particular…”
It sets the context first, then tells you what happens in that context: “I try to go to bed early.”

You could also say:

Yritän mennä aikaisin nukkumaan varsinkin maanantaisin.
This is still correct, but now the focus feels more on the trying to go early, with “especially on Mondays” almost as an afterthought.

So the chosen word order puts slightly extra emphasis on Mondays as the special case.

What exactly does maanantaisin mean, and how is it different from maanantaina?

Both relate to Monday, but they differ in frequency:

maanantaina = on Monday (this specific Monday)
- Example: Lähden maanantaina. – I’ll leave on Monday (one particular Monday).
maanantaisin = on Mondays, every Monday, usually on Mondays
- It has a repetitive / habitual meaning.
- Example: Käyn salilla maanantaisin. – I go to the gym on Mondays (as a routine).

In your sentence, maanantaisin tells us this is a regular habit or typical pattern, not just one particular Monday.

What does Varsinkin add here? Is it the same as erityisesti?

Varsinkin means “especially / in particular” and is very natural in spoken and written Finnish.

You could almost always replace it with erityisesti (“especially, particularly”), but there are small style differences:

Varsinkin often sounds a bit more colloquial and conversational.
Erityisesti can sound slightly more formal or neutral.

Both of these are fine here:

Varsinkin maanantaisin yritän mennä aikaisin nukkumaan…
Erityisesti maanantaisin yritän mennä aikaisin nukkumaan…

The meaning is practically the same.

Why is it yritän mennä and not just yritän menen?

In Finnish, verbs like yrittää (to try), haluta (to want), voida (to be able to), aikoa (to intend) are followed by the 1st infinitive form of another verb, not a finite form.

So the pattern is:

yritän mennä – I try to go
haluan mennä – I want to go
voin mennä – I can go

Using menen after yritän would be ungrammatical. You must say:

yritän mennä (never yritän menen).

Why is it nukkumaan and not nukkua after mennä?

This is a very typical Finnish construction:

mennä + -maan / -mään form of the verb

The -maan / -mään form is the 3rd (MA-) infinitive illative, and after movement verbs it often means “go (in order) to do something”.

mennä nukkumaan – to go to sleep / go to bed
tulla syömään – to come to eat
lähteä ostamaan maitoa – to go (off) to buy milk

If you said mennä nukkua, that would be incorrect. With mennä, you want nukkumaan.

What is the difference between yritän mennä nukkumaan and yritän nukkua?

They focus on different parts of the process:

yritän mennä nukkumaan
= I try to go to bed / try to go to sleep
Focus: the action of going to bed at a certain time (starting sleep).
yritän nukkua
= I try to sleep
Focus: actually sleeping, often when it’s difficult (noise, insomnia, etc.).

In your sentence, the point is about bedtime (how early you go to bed), so mennä nukkumaan is the natural choice.

Why is it aikaisin nukkumaan and not aikainen nukkumaan?

Aikaisin is an adverb meaning “early” (how/when something is done).
Aikainen is an adjective meaning “early” in front of a noun (an early something).

Menen aikaisin nukkumaan. – I go to bed early. (how? early → adverb)
aikainen aamu – an early morning (what kind of morning? → adjective)

So with verbs like mennä, you need the adverb:

mennä aikaisin (go early), herätä aikaisin (wake up early), etc.,
not mennä aikainen.

What is the difference between aikaisin and aikaisemmin? Could I say yritän mennä aikaisemmin nukkumaan?

Both are related to early, but:

aikaisin = early in an absolute sense.
- Menen aikaisin nukkumaan. – I go to bed early (in general / compared to “normal” bedtime).
aikaisemmin = earlier (comparative form).
- Menen aikaisemmin nukkumaan. – I go to bed earlier (than before / than someone else / than usual).

In your sentence, aikaisin suggests a general aim to go to bed early.
If you specifically meant earlier than I usually do, you could absolutely say:

Varsinkin maanantaisin yritän mennä aikaisemmin nukkumaan…

What exactly does muuten mean here? I’ve also seen it used like “by the way”.

Muuten has two common uses:

“Otherwise” / “or else” (conditional implication) – that’s the meaning here.
- …yritän mennä aikaisin nukkumaan, muuten olen koko päivän väsynyt.
  → I try to go to bed early, otherwise I’m tired all day.
“By the way” / “incidentally” – when introducing a side remark:
- Muuten, ootko nähnyt tämän elokuvan? – By the way, have you seen this movie?

In your sentence, it clearly means “otherwise (if I don’t)”, not “by the way”. The idea is: If I don’t go to bed early, then I’m tired all day.

Why is there a comma before muuten? Could it be a new sentence instead?

Finnish often uses a comma between two main clauses, especially when there is a linking adverb like muuten.

…yritän mennä aikaisin nukkumaan, muuten olen koko päivän väsynyt.

Here we actually have two independent clauses:

(Minä) yritän mennä aikaisin nukkumaan
(Minä) olen koko päivän väsynyt

They are linked by muuten (“otherwise”), which works similarly to English “otherwise” or “or else”.

You could also write them as two separate sentences:

Varsinkin maanantaisin yritän mennä aikaisin nukkumaan. Muuten olen koko päivän väsynyt.

Both punctuation choices are correct; the version with a comma feels a bit more connected and flowing.

Why is it koko päivän väsynyt and not koko päivä väsynyt or koko päivää väsynyt? What case is päivän?

Päivän is in the genitive singular.

The pattern koko + genitive is very common to express the whole duration of something:

koko päivän – the whole day
koko viikon – the whole week
koko vuoden – the whole year

So:

olen koko päivän väsynyt
= I am tired the whole day / all day long.

Using koko päivä väsynyt (nominative) or koko päivää väsynyt (partitive) would sound wrong in this context. With koko and a time expression indicating duration, genitive is the natural choice.

Is there a difference between olen koko päivän väsynyt and olen väsynyt koko päivän?

Both are grammatically correct and mean “I’m tired all day”, but the word order changes the emphasis slightly:

olen koko päivän väsynyt
→ Emphasis a bit more on the duration (“the whole day I’m tired”).
olen väsynyt koko päivän
→ Emphasis slightly more on the state (“I’m tired, and this lasts the whole day”).

In everyday speech and writing, both are very natural, and the difference is subtle. The original order, olen koko päivän väsynyt, is perhaps a bit more common.