Learn Hardcore Greek: Το ψυγείο είναι παλιό, όμως το μπουκάλι είναι καινούριο. - The fridge is old, however the bottle is new.

αλλά is the default coordinating "but," used like English "but": Το ψυγείο είναι παλιό, αλλά το μπουκάλι είναι καινούριο.
όμως is closer to "however/nevertheless." It’s a bit more flexible in placement and adds a slightly more contrastive, sometimes stylistic tone. In everyday speech and writing, both are fine here.

Where can I place "όμως" in this sentence?

You have three natural options, with slightly different emphasis:

At the start of the second clause: ... Όμως το μπουκάλι είναι καινούριο.
After the subject (very common): ... Το μπουκάλι όμως είναι καινούριο.
Before the subject (as in your sentence): ..., όμως το μπουκάλι είναι καινούριο.

When όμως interrupts the clause (e.g., after the subject), set it off with commas if the pause is felt: Το μπουκάλι, όμως, είναι καινούριο.

Why do the adjectives end in -ο (παλιό, καινούριο)?

Because they agree with neuter singular nouns in the nominative case:

το ψυγείο (neuter) → παλιό
το μπουκάλι (neuter) → καινούριο Greek adjectives must match the noun’s gender, number, and case.

What are the full gender forms of these adjectives?

παλιός (m), παλιά (f), παλιό (n)
καινούριος (m), καινούρια (f), καινούριο (n) There is also a widely accepted variant with a γ: καινούργιος/καινούργια/καινούργιο. Meaning is the same.

Is there a difference between "καινούριο" and "νέο"?

καινούριο = brand-new, unused, freshly made/bought.
νέο = new in contrast to old, or "young" for people (as νέος/νέα), and often used in more formal/abstract contexts (e.g., a new idea: νέα ιδέα). For a newly bought bottle, καινούριο is the natural choice.

Do I have to use the article "το" before both nouns?

Yes, normally you repeat the article with each coordinated noun: το ψυγείο και το μπουκάλι. Omitting the second article is unusual and can sound unidiomatic unless it’s a fixed expression.

Why is "είναι" used twice? Can I omit the second "είναι"?

Repeating είναι is the standard way. In very informal, headline-like, or poetic style you might see ellipsis (e.g., Το ψυγείο παλιό, το μπουκάλι καινούριο), but in normal prose you keep είναι in both clauses.

How is "είναι" conjugated? Does it change for plural?

Present tense of είμαι (to be):

εγώ είμαι, εσύ είσαι, αυτός/αυτή/αυτό είναι
εμείς είμαστε, εσείς είστε, αυτοί/αυτές/αυτά είναι Note that 3rd singular and 3rd plural are both είναι. Context tells you singular vs plural.

How do I pronounce the tricky words?

ψυγείο: [psi-ˈʝi-o] → roughly “psee-YEE-o.”
• ψ = ps, γ before ε/ι sounds like a soft “y/gh” [ʝ], ει = “ee.”
είναι: [ˈine] → “EE-neh” (the accent is on the first syllable; αι sounds like “e”).
μπουκάλι: [bu-ˈka-li] → “boo-KA-lee.”
• μπ at word start = “b,” ου = “oo.”
παλιό: [pa-ˈʎo] → “pa-LYO” (the λι yields a palatal ‘ly’ sound).
καινούριο: [ke-ˈnur-ʝo] → “ke-NOO-ryo” (the ρ + ι/γ gives a ‘ryo’ sound).
Stress marks show the stressed syllable: ψυγείο, είναι, παλιό, όμως, μπουκάλι, καινούριο.

Why is "μπ" used for a “b” sound? Isn’t β the letter for B?

In Modern Greek, β is pronounced “v.” The “b” sound is spelled μπ:

Word-initial: μπ = [b] (e.g., μπουκάλι = “bukáli”).
Inside words, μπ can sound like [mb] or [b], depending on context.

Could I say "το παλιό ψυγείο" instead of "το ψυγείο είναι παλιό"?

They’re different structures:

το παλιό ψυγείο = attributive (“the old fridge” as a noun phrase).
το ψυγείο είναι παλιό = predicative (“the fridge is old” as a full clause). Both are correct; choose based on what you want to say.

Which case are the nouns in, and why?

They’re in the nominative case because they are subjects: το ψυγείο, το μπουκάλι. Neuter nominative and accusative look identical in form, but here the role is clearly subject with είναι.

How do I make this sentence plural?

Plural nouns: τα ψυγεία, τα μπουκάλια.
Neuter plural adjectives: παλιά, καινούρια. Example: Τα ψυγεία είναι παλιά, όμως τα μπουκάλια είναι καινούρια.

Are both "καινούριος" and "καινούργιος" correct?

Yes. Both are standard. The forms with γ (καινούργιος/καινούργιο) are very common in speech; without γ (καινούριος/καινούριο) is also perfectly correct. No meaning difference.

Should there be a comma before "όμως"?

Yes, when όμως introduces a contrasting clause, you set it off with a comma: ..., όμως .... If όμως is inserted mid-clause (e.g., after the subject), surround it with commas if you hear a pause: Το μπουκάλι, όμως, είναι...

How would I say “a bottle” instead of “the bottle”?

Use the neuter indefinite article ένα:

ένα μπουκάλι = “a bottle”
το μπουκάλι = “the bottle”