Η ενυδάτωση αυξάνεται με το να προσθέτουμε νερό.

Η is the definite article in the feminine singular nominative form, so it means the.

• η ενυδάτωση = the hydration
• ενυδάτωση is a feminine noun, so it takes η in the nominative singular.

In this sentence, η ενυδάτωση is the subject.

Αυξάνεται is the 3rd person singular present middle/passive form of αυξάνω.

So grammatically it means something like:

• it increases
• it is increasing
• in some contexts, it is increased

Here it matches the singular subject η ενυδάτωση, so literally it is the hydration increases / is increased.

In Greek, the middle/passive-looking form is often used for things that undergo a change of state.

So with something like hydration, Greek commonly says:

• Η ενυδάτωση αυξάνεται = hydration increases

This does not necessarily mean there is an explicit passive idea like is increased by someone. Very often it simply means that the subject is going up or becoming greater.

So although the form looks passive, the meaning in English is often just increases.

Με το να is a very useful Greek structure meaning:

• by doing
• through doing
• by means of doing

So:

• με το να προσθέτουμε νερό = by adding water

You can think of it as a fixed pattern:

• με = with / by
• το να + verb = a nominalized doing... clause

Together, it expresses the method or means by which something happens.

This is one of the trickier parts for English speakers.

The το helps turn the να-clause into something more noun-like. In other words:

• το να προσθέτουμε νερό = the act of adding water / adding water

Then with με:

• με το να προσθέτουμε νερό = by adding water

So the το is not random; it is part of the structure that lets Greek express something similar to the English -ing form.

Because Modern Greek does not use the old infinitive as a normal everyday form the way English does.

Instead, Greek usually uses:

• να + finite verb

So where English says:

• to add
• by adding

Greek often uses a να-clause or another verbal structure.

Here:

• να προσθέτουμε is a finite verb form after να

Even though English uses an -ing form, Greek uses this different grammatical mechanism.

Προσθέτουμε is 1st person plural: we add.

In this sentence, it does not necessarily mean a specific group of people literally saying we. Greek often uses the 1st person plural in a general sense, similar to English:

• when we add water
• by adding water
• sometimes even like when you add water or when one adds water

So this is a natural way to express a general action.

Because here water is being spoken of generally, not as a specific identified quantity.

So:

• προσθέτουμε νερό = we add water
• not necessarily we add the water

If Greek wanted to refer to specific water already known in the context, it could use an article:

• προσθέτουμε το νερό = we add the water

Also, νερό here is the direct object of προσθέτουμε.

It is in the accusative singular, because it is the direct object of προσθέτουμε.

However, for many neuter nouns in Greek, the nominative and accusative forms are the same, so you just see:

• νερό

That is why there is no visible change in the noun itself.

Yes. A very common alternative would be:

• Η ενυδάτωση αυξάνεται προσθέτοντας νερό.

Here προσθέτοντας means adding, using the -οντας form.

Another possible phrasing is:

• Η ενυδάτωση αυξάνεται όταν προσθέτουμε νερό.
  • Hydration increases when we add water.

So the original sentence is grammatical and understandable, but Greek has more than one natural way to express by adding water.

Not completely. Greek word order is more flexible than English.

The given order is natural:

• Η ενυδάτωση αυξάνεται με το να προσθέτουμε νερό.

But Greek can sometimes move parts around for emphasis, for example:

• Με το να προσθέτουμε νερό, η ενυδάτωση αυξάνεται.

That puts more focus on the method: by adding water.

So the word order in Greek is flexible, but the original sentence is a normal neutral order.