When do you use UNe or UN instead of Le la or l'?

Answer 1

"Une" and "un" are undefinite articles. They are translated in English by "a - an". "Une" is to be followed by feminine nouns (une voiture: a car - une idée: an idea). "Un" is followed by masculine nouns (un bus: a bus - un évènement: an event).

Le (masc.), la (fem.), l' (both masculine or feminine - used when the following noun begins by a vowel sound) are definite articles. They are all translated by "the".

To summarize, the difference between "un - une" and "le - l' - la" is the same than between the English "a -an" and "the" and you should use these words in the same way:

- j'ai vu une voiture bleue : I saw a blue car (some or any car)

- je suis monté dans la voiture bleue : I stepped in the blue car (not in the red one).

Answer 2

"Un" and "une" are used when referring to a non-specific item or quantity, while "le," "la," and "l'" are used to refer to specific items or things. For example, you would use "un livre" (a book) when talking about any book in general, but "le livre" (the book) when referring to a specific book.