Learn Hardcore Greek: Η φίλη μου και ο φίλος της είναι χαρούμενο ζευγάρι. - My friend female and her boyfriend are a happy couple.

η (capital Η at the start of a sentence) = the for feminine nouns
- η φίλη = the (female) friend
ο = the for masculine nouns
- ο φίλος = the (male) friend

So:

Η φίλη μου = my (female) friend
ο φίλος της = her (male) friend / her boyfriend

Why is φίλη used for “friend” in the first part and φίλος in the second?

Greek changes the noun according to the person’s gender:

φίλη = female friend
φίλος = male friend

So:

η φίλη μου refers to a woman/girl.
ο φίλος της refers to a man/boy.

In this sentence, you are saying that your female friend (η φίλη μου) and her male partner (ο φίλος της) are a happy couple.

What does μου mean in η φίλη μου, and why does it come after the noun?

μου means my.

In Greek, unstressed possessive pronouns (like μου, σου, του, της, μας, σας, τους) usually go after the noun:

η φίλη μου = my friend
το βιβλίο μου = my book
ο αδελφός μου = my brother

You normally do not say η μου φίλη in modern spoken Greek. The natural order is noun + μου.

What does της mean in ο φίλος της? Whose friend/boyfriend is it?

της means her (or of her).

In this sentence the most natural interpretation is:

η φίλη μου = my (female) friend
ο φίλος της = her boyfriend (the boyfriend of that friend)

So της refers back to η φίλη μου.

The structure is:

ο φίλος της = her (male) friend / her boyfriend

Could της refer to some other woman, not to η φίλη μου?

Yes, in theory της can refer to any previously known female person.

Without context, the default reading is that της refers to the closest suitable noun: η φίλη μου.

If you wanted to make it very clear that it refers to a different woman, you would usually mention that woman explicitly before or after the sentence, for example:

Η φίλη μου και ο φίλος της Μαρίας είναι χαρούμενο ζευγάρι.
= My (female) friend and Maria’s boyfriend are a happy couple.

Here της Μαρίας removes the ambiguity.

Why is there no word for a before χαρούμενο ζευγάρι? In English we say “a happy couple.”

Greek does have an indefinite article (ένας, μία, ένα), but after the verb είμαι (to be), when we describe someone’s identity or role, it often gets dropped:

Είναι γιατρός. = He/She is a doctor.
Είναι καλό παιδί. = He/She is a good kid.
Είναι χαρούμενο ζευγάρι. = They are a happy couple.

You can say:

Είναι ένα χαρούμενο ζευγάρι.

This is also correct. Often there’s very little difference in meaning here; with ένα you might slightly emphasize that they form one such couple.

Why is χαρούμενο neuter singular, not plural or masculine/feminine?

χαρούμενο is an adjective meaning happy. Adjectives in Greek agree with the noun they directly modify, not necessarily with the real-world number of people.

Here, χαρούμενο describes ζευγάρι:

ζευγάρι = couple (grammatically neuter singular)
So the adjective must also be neuter singular:
- χαρούμενο ζευγάρι = happy couple

Even though the couple consists of two people, grammatically it is one neuter noun, so we say:

χαρούμενο ζευγάρι, not χαρούμενοι ζευγάρι.

Why is ζευγάρι neuter? It refers to people.

In Greek, grammatical gender does not always match real-world gender. Many nouns that refer to groups, things, or abstract concepts are neuter, for example:

το παιδί = the child (neuter, even for a boy or girl)
το άτομο = the person (neuter)
το ζευγάρι = the couple/pair (neuter)

So ζευγάρι is simply a neuter noun by the rules of the language, even though it refers to two human beings.

How does the verb είναι agree with the subject here? Both are singular and plural in English.

The subject is η φίλη μου και ο φίλος της = my (female) friend and her boyfriend, which is plural (they).

In modern Greek, the present tense of είμαι (to be) is:

είμαι = I am
είσαι = you are (singular)
είναι = he/she/it is
είμαστε = we are
είστε = you are (plural/polite)
είναι = they are

So είναι is used for both:

he/she/it is and
they are

That’s why you see είναι with a plural subject here. The form looks the same, but the meaning is plural because the subject is plural.

Could we just say Είναι χαρούμενοι instead of είναι χαρούμενο ζευγάρι?

Yes, but it would mean something a bit different.

Είναι χαρούμενοι. = They are happy.
Focus: the two people themselves are happy (no mention of “couple”).
Είναι χαρούμενο ζευγάρι. = They are a happy couple.
Focus: their relationship as a couple is happy; it also makes clear that they are romantically together.

So χαρούμενο ζευγάρι emphasizes their status as a couple, not just their mood.

Why is there no article before φίλη μου and φίλος της in English (we say “my friend”), but there is in Greek?

English generally does not use the with possessives:

the my friend – incorrect
my friend – correct

Greek almost always keeps the definite article even with a possessive pronoun:

η φίλη μου = literally the friend my
ο φίλος της = the friend her

So:

η / ο / το are required in Greek in these phrases,
but in English, we drop the and just say my friend, her friend/boyfriend.

Can we change the order and say Ο φίλος της και η φίλη μου είναι χαρούμενο ζευγάρι?

Yes, that is grammatically correct.

Both versions mean the same thing:

Η φίλη μου και ο φίλος της είναι χαρούμενο ζευγάρι.
Ο φίλος της και η φίλη μου είναι χαρούμενο ζευγάρι.

As in English, changing the order might very slightly change the emphasis (which person you mentally present first), but the basic meaning does not change.

Why is it και and not κι before ο φίλος της?

και means and.

In spoken and written Greek, και often becomes κι when the next word starts with a vowel sound, to make pronunciation smoother:

κι εγώ, κι εσύ, κι αυτός etc.

Before ο φίλος, both forms are possible:

Η φίλη μου και ο φίλος της…
Η φίλη μου κι ο φίλος της…

Both are correct. κι is more phonetic/colloquial; και is the full form.