"The cats drink water."
Translation:I gatti bevono l'acqua.
Good question, I would like to know the answer, too. Generally I believe it is the Italian use of the article, which is more frequent than in English. viz: We eat apples can be - Mangiamo mele, or Mangiamo le mele. But that does not explain why leaving the article off 'acqua' is wrong.
Just because you can, doesn't mean you should... in a beginning lesson on language. When I was learning French in Junior High, I only learned 'le chat' - it was years before I cared to know that one can also say, 'la chatte.' (and auto-correct just defaulted to the masculine form, as I typed it!) And I was a French major-
gli is used when the noun starts with s followed by a consonant or if the noun starts with a vowel. Ex: gli uomini (l'uomo) and gli stivali (lo stivalo). it is the plural form of "lo" and "l' ", the articles used, respectively, in front of singular male nouns beginning with s and a consonant, and singular male nouns beginning with a vowel.
Il, gli and i are the articles that you have to use when you are reffering to male words. Il and l' are used for singular nouns, gli and i for the plural ones. La is the article you have to use when you're referring to a female noun. Le is for the plural female nouns. You have to learn and memorize just by training which words need one type of article or another.
Il is before a masculine singular (libro), gli (pronounced lee i think) is before any plural starting with a vowel (gli animali), "i" is before a regular masculine plural (i gatti), le is before a feminine plural (le donne), la is before a feminine singular (la ragazza), and l' is before a singular noun starting with a vowel (l'uomo)
since gatto is masculine, it would be I gatti because "le" is the feminine plural article