Στον νεροχύτη της κουζίνας υπάρχουν δύο ποτήρια, και η χτένα μου είναι ακόμα εκεί από το πρωί.

Στον is the very common contracted form of σε + τον.

Greek regularly combines σε with the definite article:

• σε + τον → στον
• σε + τη(ν) → στη(ν)
• σε + το → στο

So στον νεροχύτη literally corresponds to in / at the sink.

Also, after σε, Greek uses the accusative case, even for location.

The basic dictionary form is ο νεροχύτης. That is the nominative singular.

After σε, Greek uses the accusative, so it becomes:

• nominative: ο νεροχύτης
• accusative: τον νεροχύτη

Because στον already contains τον, the full phrase is στον νεροχύτη.

Της κουζίνας is the genitive singular of η κουζίνα.

Greek often uses the genitive to mean of the ... or to show what something belongs to or is associated with. So:

• ο νεροχύτης της κουζίνας = the sink of the kitchen = the kitchen sink

This is a very common pattern in Greek:

• η πόρτα του σπιτιού = the door of the house
• το χρώμα του αυτοκινήτου = the color of the car

Υπάρχουν is the normal verb for there are / there exist.

So:

• υπάρχουν δύο ποτήρια = there are two glasses

By contrast, είναι usually means are / is in the sense of identity, description, or location of a specific subject.

For example:

• Τα ποτήρια είναι στον νεροχύτη = The glasses are in the sink
• Στον νεροχύτη υπάρχουν δύο ποτήρια = There are two glasses in the sink

In your sentence, Greek is introducing the existence of the glasses in that location, so υπάρχουν fits very naturally.

Because the thing that exists is plural: δύο ποτήρια.

Greek verbs agree in number with their subject:

• υπάρχει ένα ποτήρι = there is one glass
• υπάρχουν δύο ποτήρια = there are two glasses

So υπάρχουν is plural because ποτήρια is plural.

Because it means two glasses, not the two glasses.

Greek often leaves out the article with indefinite quantities:

• ένα ποτήρι = a glass
• δύο ποτήρια = two glasses

If you wanted to say the two glasses, you could say τα δύο ποτήρια.

So:

• υπάρχουν δύο ποτήρια = there are two glasses
• υπάρχουν τα δύο ποτήρια would be much more specific and usually would not fit this context

Ποτήρια is the neuter plural form of το ποτήρι.

Forms:

• singular: το ποτήρι
• plural: τα ποτήρια

In this sentence, δύο ποτήρια is both the nominative and accusative plural form, since many neuter nouns have the same form in those cases.

Greek normally uses the definite article with possessed nouns.

So Greek prefers:

• η χτένα μου = my comb
• το βιβλίο μου = my book
• ο φίλος μου = my friend

This is different from English, where my usually replaces the. In Greek, the article is usually still there.

So η χτένα μου is the normal way to say my comb.

Because μου here is a weak possessive pronoun and it normally comes after the noun.

So:

• η χτένα μου = my comb
• το σπίτι μου = my house

If you want extra emphasis, Greek can use δικός:

• η δική μου χτένα = my comb, with stronger emphasis

But in an ordinary sentence, η χτένα μου is the standard form.

Here ακόμα means still.

So είναι ακόμα εκεί means is still there.

You may also see the spelling ακόμη. In most everyday contexts, ακόμα and ακόμη mean the same thing.

Examples:

• Είναι ακόμα εδώ = He/She/It is still here
• Δεν έχω φάει ακόμα = I have not eaten yet

So the exact English translation depends on context: still or yet.

Εκεί means there, and it points back to the previously mentioned location, namely the sink.

Greek often uses a word like εκεί to make the connection explicit:

• η χτένα μου είναι ακόμα εκεί = my comb is still there

Without εκεί, the sentence would still be grammatical, but it would lose that clear link to the place already mentioned. Including it sounds natural and helps show that the comb is in the same location.

Literally, it means from the morning, but in natural English it usually means since the morning or since this morning.

So in context:

• είναι ακόμα εκεί από το πρωί = it is still there from this morning / it has been there since this morning

This suggests that the comb was there in the morning and remains there now.

Από takes the accusative in Modern Greek.

So:

• το πρωί is accusative here

You can think of it as:

• από + το πρωί = from the morning

This is normal for modern Greek prepositions such as σε, από, and με, which generally take the accusative.

Yes, it is very natural.

Greek word order is more flexible than English word order. Starting with Στον νεροχύτη της κουζίνας puts the location first and sets the scene:

• Στον νεροχύτη της κουζίνας υπάρχουν δύο ποτήρια
  In the kitchen sink, there are two glasses.

This is a very common Greek pattern when introducing something in a place. You could also rearrange parts of the sentence, but the version you have sounds natural and well-balanced.

Yes. Μέσα στον νεροχύτη means inside the sink and is a little more explicit.

• στον νεροχύτη can mean in / at the sink, depending on context
• μέσα στον νεροχύτη clearly means inside the sink basin

In many everyday situations, just στον νεροχύτη is enough, because the context already makes the meaning clear.

Yes, because the articles and some forms depend on gender.

In this sentence:

• ο νεροχύτης = masculine
• η κουζίνα = feminine
• το ποτήρι = neuter
• η χτένα = feminine

That is why you get:

• στον for masculine accusative singular
• της κουζίνας for feminine genitive singular
• δύο ποτήρια for neuter plural
• η χτένα μου for feminine singular

Learning each noun together with its article is very helpful in Greek.