The indefinite article has three genders: masculine, feminine and neuter and it is used when the speaker refers to a person, animal or object which is indefinite and unknown or is introduced for the first time, for example:
Είδα μια αρκούδα στο βουνό. – I saw a bear on the mountain.

Notice that the indefinite article has no plural form, indefinite pronouns can be used instead.

Like with the definite article, the final ν of the article is used when the following word starts with a vowel or the consonants: ξ,π,κ,τ,ψ,τς,τζ,γκ,ντ,μπ

Attention!

Do not confuse the indefinite article with the numeral.

Example: Έχει μόνο ένα πόδι = He has only one leg

Uses of the indefinite article

1. To express generalness like the properties of a noun

Example: Μια πέτρα ειναι άκαμπτη = A/All/Every stone is rigid

2. With months, days, seasons, dates to denote a non-specific point in time

Examples: Έχω να σε δώ μια εβδομάδα = I haven’t seen you for a week.

Μια μέρα κόντεψα να σκοτωθώ = One day I almost got killed.

3. To give emphasis

Example: Είχα έναν πόνο που δεν θα τον άντεχες = I had such a pain that you couldn’t stand it.

4. With uncountable nouns

Example: Θα ήθελα έναν καφέ παρακαλώ = I would like a coffee, please.

5. In front of certain pronouns like τέτοιος, άλλος, δικό μου, in all genders and all cases

Example: Είναι απαράδεκτη μια τέτοια συμπεριφορά = Such behavior is unacceptable.


Below are some examples to show how each noun is formed depending on gender and case

Masculine: ένας άνδρας (a man)

Singular

Nominative Case -->ένας άνδρας
Genitive Case -->ενός άνδρα
Accusative Case -->έναν άνδρα

Feminine: μια μητέρα (a mother)

Singular

Nominative Case -->μια μητέρα
Genitive Case -->μιας μητέρας
Accusative Case -->μια μητέρα

Neuter: ένα κορίτσι (a girl)

Singular

Nominative Case -->ένα κορίτσι
Genitive Case -->ενός κοριτσιού
Accusative Case -->ένα κορίτσι