Learn Italian: Il tuo treno ha diciassette posti liberi. - Your train has seventeen free seats.

In Italian, numbers 11 through 16 end with -dici (like undici for 11 or dodici for 12). But starting at 17, the pattern flips! The 'ten' part comes first, followed by the second digit. So dieci (10) plus sette (7) becomes diciassette. Pay special attention to the spelling: it gets a double s and a double t!

Why do we need il in il tuo treno? Doesn't that mean 'the your train'?

Exactly, it literally translates to 'the your train'. In Italian, you almost always have to use a definite article (like il) before a possessive word like tuo. The main exception is when you are talking about a single family member (like mio fratello for 'my brother').

Why is the adjective liberi at the end of the sentence?

In Italian, descriptive adjectives like liberi (free or available) usually go after the noun they describe, which is posti (seats) here. Notice that both words end in -i because they are masculine and plural.

I know ha means 'has', but why is the 'h' silent?