If English is your first and only language so far, this lesson might be a little hard for you to swallow.
In English we have one word to say "the". It doesn't matter what you're talking about, it doesn't matter how many of them there are. It's always the same word.
See? It's the same.
But in Italian there are SEVEN words for "the", depending on what you're talking about. SEVEN! Here they are:
Why so many? It's because the word you use for "the" changes depending on whether you're talking about something that is masculine or feminine.
There's no particular rhyme or reason to whether something is masculine or feminine ... it's just something you learn when you learn each word.
The second thing that determines which word you use is whether you're talking about a single thing, or multiple things. Dog, or dogs?
The third thing is whether the thing you're talking about starts with certain letters.
Don't be discouraged! Italian is still one of the easiest languages to learn, and this is a simple rule just requires a little bit of practice.
When you're talking about things that are, for whatever reason, feminine, use the following rules:
la is used for all feminine singular (just one) nouns beginning with a consonant.
When that singular feminine noun starts with a vowel instead, la contracts into l’.
Are you looking at more than one of something? Then you use le. Le is used for all feminine plural nouns, even if they start with a vowel.
il is used for masculine singular (just one) nouns beginning with a consonant.
l’ is used for masculine singular nouns starting with a vowel.
When you've got more than one thing, you'll use either i or gli. I is used for masculine plural nouns starting with a consonant.
gli is used for masculine plural nouns starting with a vowel.
In addition to the rules above, there is a special case for masculine nouns that start with a "Z" or an "S-consonant". (That's words that start "St", "Sc", "Sp" etc. Not words that start "Sa", "Si", "Se" etc.)
lo is used for masculine singular nouns beginning with a Z or S+consonant.
gli is used for masculine plural nouns beginning with a Z or S+consonant (plus vowels, as above)
That might seem like a whole lot of things to remember! The easiest way to do it is to learn the definite article for a word at the same time as you learn the word itself. Don't just learn house = casa. Learn house = la casa. That will tie them together in your memory.