Αυτός είναι ο αδερφός μου.

to be

Breakdown of Αυτός είναι ο αδερφός μου.

• μου: my
• ο αδερφός: the brother
• αυτός: it

Questions & Answers about Αυτός είναι ο αδερφός μου.

Why does the sentence start with Αυτός? Could you just say Είναι ο αδερφός μου?

Αυτός means this (man) or he and is the subject of the sentence.

• Αυτός είναι ο αδερφός μου = This is my brother / He is my brother.
• Είναι ο αδερφός μου = He is my brother (more like He’s my brother, without pointing or strong emphasis).

In Greek, subject pronouns (like αυτός, αυτή, εγώ, εσύ) are often dropped because the verb ending already shows the person.
You keep Αυτός when you:

• want to point someone out (this one here is my brother), or
• want to contrast or emphasize (He is my brother (not someone else)).

So yes, you can say Είναι ο αδερφός μου, but it slightly changes the feel: less pointing, more simple statement.

Why is it Αυτός (masculine) and not Αυτή or Αυτό?

Greek demonstrative pronouns agree in gender with the person or thing you are referring to.

• Αυτός = this man/he (masculine)
• Αυτή = this woman/she (feminine)
• Αυτό = this thing/it or this child (neuter)

Because αδερφός (brother) is a masculine noun, you use the masculine form Αυτός.

If you were saying This is my sister, you would say:

• Αυτή είναι η αδερφή μου.

What is the function of είναι in this sentence?

Είναι is the 3rd person singular of the verb είμαι (to be).

• είμαι = I am
• είσαι = you are (singular)
• είναι = he/she/it is

So Αυτός είναι ο αδερφός μου literally = This-he is the brother my.

Greek needs the verb είμαι here just like English needs is in This is my brother; you cannot normally omit it in a simple statement like this.

Why do we say ο αδερφός with ο? In English we don’t say the brother my.

Greek uses the definite article (ο, η, το) much more often than English, especially:

• with nouns in general: ο άντρας (the man), η γυναίκα (the woman)
• with family members: ο αδερφός μου, η μητέρα μου, ο πατέρας μου

So:

• ο αδερφός μου literally = the brother my, but in natural English it’s just my brother.

In Greek, ο shows that this is a specific, known brother.
If you drop ο and say αδερφός μου, it sounds incomplete or wrong in most contexts. The article is normally required here.

Why is μου placed after αδερφός instead of before, like English my brother?

In Greek, the unstressed possessive pronouns (my, your, his, her, our, your, their) usually come after the noun and behave like clitics (they attach closely):

• ο αδερφός μου = my brother
• η μητέρα σου = your mother
• το σπίτι του = his house

So the natural order is:

(article) + noun + possessive-pronoun

English puts my before the noun; Greek puts μου after it.

Is μου always unstressed like this? Can it ever come before the noun?

There are two main patterns:

1. Unstressed (normal possession, after the noun)

   • ο αδερφός μου = my brother
   • το βιβλίο σου = your book

2. Stressed (for emphasis, before the noun, often with δικός)

   • ο δικός μου αδερφός ≈ my own brother / my brother (as opposed to someone else’s)
   • η δική σου μητέρα ≈ your own mother / your mother (not mine)

So:

• Everyday, neutral: ο αδερφός μου
• Emphatic contrast: ο δικός μου αδερφός

What is the difference between αδερφός and αδελφός?

Both mean brother.

• αδελφός = the more traditional / formal / dictionary spelling
• αδερφός = the more phonetic, common modern spelling in everyday writing

In modern pronunciation, they sound the same (or very close), so you will see both.
For learning purposes, you can treat them as the same word; just be aware that both forms exist.

Why is it ο αδερφός and not τον αδερφό?

This is about case in Greek.

• ο αδερφός = nominative (used for the subject of the sentence)
• τον αδερφό = accusative (used for the direct object)

In Αυτός είναι ο αδερφός μου:

• ο αδερφός is the part that renames Αυτός (it’s the subject complement), so it is in the nominative: ο αδερφός.

You’d use τον αδερφό when it is the object:

• Βλέπω τον αδερφό μου. = I see my brother.

Why does ο have to be masculine? How do I know which article to use?

The article agrees with the gender, number, and case of the noun.

For αδερφός:

• Gender: masculine
• Number: singular
• Case: nominative (subject)

So you use the masculine, singular, nominative article ο:

• ο αδερφός (the brother)
• η αδερφή (the sister – feminine, so η)
• το παιδί (the child – neuter, so το)

To know which article to use, you need to learn the gender of each noun as you learn the word:

• ο αδερφός (m.)
• η αδερφή (f.)
• το σπίτι (n.)

How would the sentence change if I were talking about a sister instead of a brother?

You must change everything that depends on gender:

• Αυτή είναι η αδερφή μου. = This is my sister.

Changes:

• Αυτός → Αυτή (masculine → feminine)
• ο → η (masculine article → feminine article)
• αδερφός → αδερφή (brother → sister)
• μου stays the same (possessive my does not change with gender).

Can this sentence also mean He is my brother, or is it only This is my brother?

Context decides.

Αυτός είναι ο αδερφός μου can be understood as:

• This is my brother (most natural if you are pointing at someone), or
• He is my brother (if it’s already clear who he is from the context).

Because Αυτός can function both as:

• a demonstrative (this (man)) and
• a personal pronoun (he),

both translations are possible. In everyday situations where you introduce someone you’re pointing to, it’s normally taken as This is my brother.

How do you pronounce Αυτός είναι ο αδερφός μου?

Approximate pronunciation (in English-style syllables, stressed syllable in capitals):

• Αυτός → af-TÓS (the υ after αφ sounds like f, so af)
• είναι → Í-ne (two syllables: EE-neh)
• ο → o (like o in not, but a bit shorter/tenser)
• αδερφός → a-ther-FÓS (the δ is like the th in this, then fos with stress)
• μου → mu (like moo, but shorter)

Altogether, with smooth rhythm:

af-TÓS Í-ne o a-ther-FÓS mu.