Το καινούριο σαμπουάν είναι ωραίο, αλλά προτιμώ εκείνο που χρησιμοποιεί η αδερφή μου.

Το is the definite article meaning the.

In Greek, nouns usually appear with an article much more often than in English, and the article must agree with the noun in gender, number, and case.

Here:

• το = the for a neuter singular noun
• σαμπουάν is treated as neuter singular
• καινούριο also matches that neuter singular form

So:

• το σαμπουάν = the shampoo
• το καινούριο σαμπουάν = the new shampoo

If you wanted a new shampoo, you would usually say:

• ένα καινούριο σαμπουάν

Because καινούριο has to agree with σαμπουάν.

Greek adjectives change form depending on the noun they describe:

• καινούριος = masculine
• καινούρια / καινούργια = feminine
• καινούριο / καινούργιο = neuter

Since σαμπουάν is neuter, the adjective is also neuter:

• το καινούριο σαμπουάν

The same thing happens later with ωραίο:

• το σαμπουάν είναι ωραίο

Yes. Σαμπουάν is a loanword (from French originally), and in Greek it is commonly treated as an indeclinable neuter noun.

That means its form usually stays the same:

• το σαμπουάν
• του σαμπουάν
• τα σαμπουάν

So even though it does not have the typical Greek noun ending, Greek still treats it grammatically as neuter.

Yes, ωραίο here means something like:

• nice
• good
• pleasant
• pretty good

It agrees with σαμπουάν, so it appears in the neuter singular form:

• masculine: ωραίος
• feminine: ωραία
• neuter: ωραίο

So:

• Το σαμπουάν είναι ωραίο = The shampoo is nice / good

In everyday Greek, ωραίος / ωραία / ωραίο is very common and flexible.

Yes, νέο σαμπουάν is possible.

Both καινούριο and νέο can mean new, but they are not always identical in feeling:

• καινούριο often emphasizes brand-new, newly bought, or not old / not used
• νέο can mean new, but it can also mean recent, modern, or another/new one

So:

• το καινούριο σαμπουάν often sounds like the new shampoo in the sense of the new one
• το νέο σαμπουάν is also correct, but may feel a bit more neutral or formal depending on context

In everyday speech, καινούριο is very common when talking about objects.

Because Greek verbs usually show the subject clearly by their ending.

προτιμώ means I prefer.
The ending -ώ tells you the subject is I.

So Greek often leaves out subject pronouns unless there is special emphasis or contrast.

• προτιμώ = I prefer
• εγώ προτιμώ = I prefer / I’m the one who prefers, with extra emphasis

This is very normal in Greek.

Εκείνο means that one here.

Greek often uses demonstratives like this instead of repeating the noun:

• εκείνο = that one (neuter singular)

So:

• προτιμώ εκείνο = I prefer that one

Because σαμπουάν is neuter singular, the demonstrative is also neuter singular:

• masculine: εκείνος
• feminine: εκείνη
• neuter: εκείνο

You could say the full noun again, but it is less natural if the noun is already obvious:

• προτιμώ εκείνο το σαμπουάν
• προτιμώ το σαμπουάν που χρησιμοποιεί η αδερφή μου

The sentence chooses the more natural shorter option: εκείνο.

Here που introduces a relative clause. It works like that, which, or the one that in English.

So:

• εκείνο = that one
• που χρησιμοποιεί η αδερφή μου = that my sister uses

Together:

• εκείνο που χρησιμοποιεί η αδερφή μου = the one that my sister uses

A useful way to understand it is:

• προτιμώ εκείνο = I prefer that one
• ποιο εκείνο; = which one?
• εκείνο που χρησιμοποιεί η αδερφή μου = the one that my sister uses

In Greek, που is a very common and simple relative word.

Both are possible, but που χρησιμοποιεί η αδερφή μου is very natural Greek.

Greek word order is more flexible than English because the verb endings and articles help show the grammar. In relative clauses, it is very common for the verb to come before the subject.

So both can mean the same thing:

• που χρησιμοποιεί η αδερφή μου
• που η αδερφή μου χρησιμοποιεί

The first version often sounds more natural and flowing in everyday Greek.

You know from the article and the structure.

• η αδερφή μου is in the nominative form, so it is the subject: my sister
• χρησιμοποιεί = uses
• The thing being used is understood as εκείνο / that one

So the meaning is:

• the one that my sister uses

Not:

• the one that uses my sister

Greek can place the subject after the verb, but the grammar still shows who is doing the action.

Because η αδερφή μου is the normal way to say my sister when it is the subject.

Breakdown:

• η αδερφή = the sister
• μου = my

Greek usually places the unstressed possessive word μου after the noun:

• η αδερφή μου = my sister
• το βιβλίο μου = my book
• ο φίλος μου = my friend

This is the standard pattern.

Yes. Both exist, but they differ in style and usage.

• αδερφή is the very common modern everyday form
• αδελφή is more formal, older, or sometimes associated with more careful/literary language

The same applies to:

• αδερφός / αδελφός

In ordinary spoken Greek, αδερφή is extremely common.

Because εκείνο is already standing on its own as a pronoun: that one.

Compare:

As an adjective before a noun:

• εκείνο το σαμπουάν = that shampoo

As a pronoun by itself:

• εκείνο = that one

In this sentence, Greek uses the pronoun form:

• προτιμώ εκείνο που χρησιμοποιεί η αδερφή μου
• I prefer the one that my sister uses

So there is no need to repeat το σαμπουάν.

Yes, but it would not mean exactly the same thing in every context.

• εκείνο usually means that one
• αυτό usually means this one or sometimes that one, depending on context

Greek demonstratives work partly like English:

• αυτό = this
• εκείνο = that

So if you are contrasting two shampoos, εκείνο makes sense for that one.
If the shampoo feels closer in the conversation or physically near the speaker, αυτό could also be used.

In this sentence, εκείνο fits the contrast very naturally:

• This new shampoo is nice, but I prefer that one...

It is the most common word for but in everyday Greek.

So:

• ωραίο, αλλά προτιμώ... = nice, but I prefer...

There are other ways to express contrast in Greek, but αλλά is the basic everyday conjunction you should learn first.

Yes, that is a very literal breakdown, and it can help you understand the structure.

Word-for-word-ish:

• Το καινούριο σαμπουάν = The new shampoo
• είναι ωραίο = is nice
• αλλά = but
• προτιμώ = I prefer
• εκείνο = that one
• που χρησιμοποιεί η αδερφή μου = that my sister uses

Natural English:

• The new shampoo is nice, but I prefer the one my sister uses.

So your literal understanding is useful for grammar, even if the natural English translation is smoother.

A very natural full version would be:

• Το καινούριο σαμπουάν είναι ωραίο, αλλά προτιμώ το σαμπουάν που χρησιμοποιεί η αδερφή μου.

This is grammatically fine, but it sounds a bit more repetitive.

Greek, like English, often prefers to avoid repeating an obvious noun:

• the shampoo ... I prefer the one my sister uses instead of
• the shampoo ... I prefer the shampoo my sister uses

So the original sentence sounds more natural.

A few useful points:

• καινούριο: the stress is on νού
• σαμπουάν: the stress is on the last syllable, -άν
• ωραίο: the stress is on αί
• προτιμώ: the stress is on the last syllable, -μώ
• εκείνο: the stress is on κεί
• χρησιμοποιεί: the stress is on the last εί
• αδερφή: the stress is on the last syllable, -φή

Also, in natural speech, Greek flows quite smoothly:

• Το καινούριο σαμπουάν είναι ωραίο
• αλλά προτιμώ εκείνο που χρησιμοποιεί η αδερφή μου

Listening practice helps a lot with these stress patterns, because stress is very important in Greek.