Learn Hardcore Finnish: Jos hikoilet paljon, muista juoda tarpeeksi vettä. - If you sweat a lot, remember to drink enough water.

jos = if (condition, not certain it will happen)
- Jos sataa, pysyn kotona. – If it rains, I’ll stay home.
kun = when/whenever (something expected/known to happen)
- Kun sataa, pysyn kotona. – When it (typically) rains, I stay at home.

In everyday speech, jos and kun sometimes overlap, but in a sentence giving a conditional piece of advice like this, jos is the clearest choice.

Why is there a comma after paljon?

Finnish uses a comma between a subordinate clause and the main clause.

Jos hikoilet paljon, → subordinate clause (condition)
muista juoda tarpeeksi vettä. → main clause (the thing you should do)

So the comma marks the boundary:

Jos hikoilet paljon, muista juoda tarpeeksi vettä.

You would also use a comma if you reversed the order:

Muista juoda tarpeeksi vettä, jos hikoilet paljon.

Where is the word “you”? Why is there no separate pronoun for “you”?

Finnish normally drops subject pronouns because the verb ending already shows the person.

hikoilet = you sweat (2nd person singular)
- stem: hikoile-
- ending: -t (you, singular)
muista = (you) remember! (imperative 2nd person singular)

So the subject “you” is built into the verb forms and doesn’t need to be said:

Jos hikoilet paljon, muista juoda…
Literally: If sweat-you a lot, remember-to drink…

You can say sinä hikoilet to emphasize you, but it’s unnecessary here:

Jos *sinä hikoilet paljon, muista juoda… (adding emphasis on *you in contrast to others).

Why is hikoilet in the normal present tense, and not a conditional form like hikoilisit?

Hikoilet is in the present indicative: you sweat / you are sweating.

This is the standard tense for expressing general conditions or typical situations:

Jos hikoilet paljon, … – If you sweat a lot, … (whenever that happens / generally speaking)

The conditional hikoilisit would mean you would sweat, and would suggest something more hypothetical or dependent on another condition. That doesn’t fit well here, because sweating a lot is the condition, not something hypothetical caused by something else.

So present indicative is the natural choice for:

general truths
repeated situations
typical conditions that may occur in real life

What form is muista, and why isn’t it muistat?

Muista here is the imperative 2nd person singular of muistaa (to remember).

muistat = you remember (a statement, indicative)
muista! = remember! (a command/instruction, imperative)

This sentence is giving advice:

Muista juoda tarpeeksi vettä.
= Remember to drink enough water.

So the imperative muista is used to tell someone what they should do.
If you said muistat juoda tarpeeksi vettä, it would mean you remember to drink enough water (just stating a fact), not giving advice.

Why is it muista juoda and not muista juot or muista, että juot?

In Finnish, some verbs (like muistaa – to remember, haluta – to want, alkaa – to start) are often followed by another verb in its basic infinitive form to express remember to do X:

muista juoda = remember to drink
(juoda = the basic infinitive “to drink”)

Patterns:

muistan juoda vettä – I remember to drink water.
yritän oppia suomea – I try to learn Finnish.

Using juot would be wrong here because juot is a finite verb (you drink) and you don’t normally chain two finite verbs like that:

✗ muista juot → incorrect

You can say:

Muista, että juot tarpeeksi vettä.
= Remember that you drink enough water.

But that’s more clumsy and not the usual natural way to express this advice. Muista juoda tarpeeksi vettä is the standard and most natural structure.

Why is juoda in the basic infinitive and not something like juomaan?

Finnish has several infinitive types. Here, juoda is the 1st infinitive (dictionary form).

With verbs like muistaa (remember), haluta (want), aikoa (intend), voida (can), etc., the normal pattern to express remember/want/plan to do something is:

[verb] + 1st infinitive

Examples:

Haluan syödä. – I want to eat.
Muistan soittaa. – I remember to call.
Voit tulla. – You can come.

Juomaan is an illative form of the 3rd infinitive, and it has a slightly different feel, often implying going into the activity:

Menin juomaan vettä. – I went (in order) to drink water.

Here the simple remember to drink is best expressed with juoda.

What exactly does paljon do in this sentence?

Paljon is an adverb meaning “a lot, much”.

It modifies the verb hikoilet:

hikoilla paljon = to sweat a lot / to sweat heavily

So:

Jos hikoilet paljon, …
= If you sweat a lot, …

You could drop paljon and still have a grammatically correct sentence:

Jos hikoilet, muista juoda tarpeeksi vettä.

But then it would sound more general: If you sweat (at all / in general)… rather than specifically a lot.

What does tarpeeksi mean, and why is it placed before vettä?

Tarpeeksi is an adverb meaning “enough” (literally: sufficiently).

In this sentence:

juoda tarpeeksi vettä = to drink enough water

The structure is:

juoda – to drink
tarpeeksi – enough (adverb, describes how much)
vettä – water (partitive, because it’s an unspecified amount)

You could also place tarpeeksi later with a slight change in emphasis:

juoda vettä tarpeeksi – drink water enough

Both are grammatically correct, but juoda tarpeeksi vettä is very natural and common.

Why is vettä in the partitive case and not just vesi?

Vettä is the partitive singular of vesi (water).

Finnish uses the partitive for indefinite/uncountable quantities, especially with verbs like juoda (to drink) when you’re not talking about a specific, countable object but some amount of a substance.

juoda vettä = to drink (some) water
syödä leipää = to eat (some) bread

Here you’re not talking about all the water or a specific glass of water, just enough water in general, so partitive is used.

Using nominative vesi here (e.g. juoda vesi) would normally suggest a specific, bounded amount:

juoda vesi – drink the water (e.g. all of the water in some specific glass/bottle)

That’s not what this general health advice is talking about, so vettä in the partitive is the correct and natural choice.

Could I say Jos kun hikoilet paljon… or use kun instead of jos?

You should use either jos or kun, not both:

Jos hikoilet paljon, … – If you sweat a lot, …
Kun hikoilet paljon, … – When(ever) you sweat a lot, …

Using jos kun together is incorrect.

The difference:

jos: focuses on the condition; it may or may not happen.
Good for conditional advice like in this sentence.
kun: often used for things that do happen or are expected; more like when you (do), then…

In health advice like this, jos is the most straightforward choice because it clearly states: If this condition applies to you, then do this.

Is the sentence formal or informal? How would I say this politely to a group or in general advice?

The current sentence is 2nd person singular, so it feels like addressing one person directly and somewhat informally/neutral:

Jos hikoilet paljon, muista juoda tarpeeksi vettä.

For talking to several people at once, you’d use plural imperative:

Jos hikoilette paljon, muistakaa juoda tarpeeksi vettä.
= If you (plural) sweat a lot, remember to drink enough water.

For general, impersonal advice (e.g., in a brochure or article), Finnish often uses an impersonal/passive construction:

Jos hikoilee paljon, kannattaa muistaa juoda tarpeeksi vettä.
= If one sweats a lot, it’s good to remember to drink enough water.

All are correct; the choice depends on whether you’re addressing one person, many people, or giving general advice.