Learn Hardcore Greek: Ο σκύλος είναι μαύρος, αλλά η γάτα είναι άσπρη.

Meaning:
- Animals often default to one gender: σκύλος (dog) is usually masculine, γάτα (cat) is usually feminine.
- If you need to specify biological sex, you can say ο αρσενικός σκύλος (the male dog) / η θηλυκιά γάτα (the female cat), etc.
Form (typical endings):
- Many masculine nouns end in -ος → σκύλος
- Many feminine nouns end in -α or -η → γάτα

These patterns have many exceptions, so you usually learn each noun together with its article:
ο σκύλος, η γάτα, το σπίτι (house), etc.

Why is it μαύρος but άσπρη? Why don’t the adjectives look the same?

Adjectives in Greek agree with the noun in gender, number, and case.
The basic adjective pattern here is:

μαύρος, μαύρη, μαύρο (black – masc., fem., neut.)
άσπρος, άσπρη, άσπρο (white – masc., fem., neut.)

So:

ο σκύλος είναι μαύρος
- σκύλος is masculine → use masculine form μαύρος
η γάτα είναι άσπρη
- γάτα is feminine → use feminine form άσπρη

If the nouns were neuter, you’d use μαύρο, άσπρο instead.

Can the adjectives come before the noun, like in English: ο μαύρος σκύλος?

Yes. Greek adjectives often come before the noun:

ο μαύρος σκύλος = the black dog
η άσπρη γάτα = the white cat

In your sentence, the structure is NOUN + είναι + ADJECTIVE (the dog is black), so the adjective naturally comes after the verb. But when the adjective directly modifies the noun, both orders exist, with slightly different uses:

ο μαύρος σκύλος – the black dog (describing a type/quality of dog)
ο σκύλος είναι μαύρος – the dog is black (making a statement about this particular dog)

Both are common and correct; context decides which sounds better.

What exactly does είναι mean, and why doesn’t it change between ο σκύλος and η γάτα?

είναι is the 3rd person form of the verb είμαι (to be).
It’s used for he/she/it is and they are. The present tense of είμαι is:

(εγώ) είμαι – I am
(εσύ) είσαι – you are (singular)
(αυτός/αυτή/αυτό) είναι – he / she / it is
(εμείς) είμαστε – we are
(εσείς) είστε – you are (plural / polite)
(αυτοί/αυτές/αυτά) είναι – they are

So είναι is used both for:

ο σκύλος είναι… – the dog is…
η γάτα είναι… – the cat is…

and also for plurals:

οι σκύλοι είναι… – the dogs are…

Could I leave out είναι and just say Ο σκύλος μαύρος, αλλά η γάτα άσπρη?

In standard, correct Greek, you should not omit είναι here. The normal sentence is:

Ο σκύλος είναι μαύρος, αλλά η γάτα είναι άσπρη.

Omitting είναι can sometimes occur in very informal speech or certain fixed expressions, but it is not the general rule (unlike in some other languages).

For learners, it’s best to always include the correct form of είμαι in such sentences.

What’s the role of αλλά? Are there other words for but?

αλλά means but and introduces a contrast:

Ο σκύλος είναι μαύρος, αλλά η γάτα είναι άσπρη.
→ The dog is black, but the cat is white.

Other common ways to express but / however:

μα – also but, more informal/colloquial:
- Ο σκύλος είναι μαύρος, μα η γάτα είναι άσπρη.
όμως – however / but; usually not placed between two parallel clauses in the same way as αλλά, but as an extra word:
- Ο σκύλος είναι μαύρος. Η γάτα, όμως, είναι άσπρη.

In this exact sentence, αλλά is the most neutral and common choice.

How do you pronounce γάτα and the letter γ in general?

In γάτα:

γ is pronounced like a soft g, similar to a French g in guerre, or like an English g in go but a bit softer.
γάτα is [ˈɣa.ta].

The pronunciation of γ depends on the following vowel:

Before α, ο, ου → a voiced velar fricative [ɣ], as in γάλα (milk), γόνατο (knee), γούνα (fur).
Before ε, αι, ι, η, υ, ει, οι → the sound moves a bit forward in the mouth, [ʝ], similar to the English y in yes, but voiced and fricative: γεια (hi), γύρος, etc.

So γάτα starts with this soft ɣ sound.

What about άσπρη—why is there a consonant cluster σπρ and how is it pronounced?

άσπρη is pronounced [ˈaspri]:

ά – [a], as in father
σπρ – [spr], a single cluster: you say s
- p
  - r smoothly together
η – here pronounced [i], like ee in see

Greek often allows consonant clusters like σπρ, στρ, σκλ, etc. They may feel tricky at first, but you pronounce them without inserting a vowel between the consonants:

σπρ as in άσπρη
στρ as in στρόφιγγα
σκλ as in σκληρός

Are μαύρος and άσπρος the only words for black and white in Greek?

They’re the most common everyday adjectives:

μαύρος, μαύρη, μαύρο – black
άσπρος, άσπρη, άσπρο – white

There are also more formal or alternative words:

μέλας, μέλαινα, μέλαν – archaic/formal black (seen in learned or poetic contexts)
λευκός, λευκή, λευκό – formal or neutral white (e.g. λευκό κρασί – white wine; λευκή μπλούζα – white blouse)

In ordinary conversation about a dog and a cat, μαύρος and άσπρος are exactly what you would use.

How would the sentence change in the plural: The dogs are black, but the cats are white?

You need to make nouns, articles, adjectives, and verb plural:

Ο σκύλος είναι μαύρος → Οι σκύλοι είναι μαύροι
- ο → οι (masc. plural)
- σκύλος → σκύλοι (plural of σκύλος)
- μαύρος → μαύροι (masc. plural)
η γάτα είναι άσπρη → Οι γάτες είναι άσπρες
- η → οι (fem. plural)
- γάτα → γάτες (plural of γάτα)
- άσπρη → άσπρες (fem. plural)

Remember that είναι stays the same for they are.

Full plural sentence:

Οι σκύλοι είναι μαύροι, αλλά οι γάτες είναι άσπρες.