Learn Italian: Il treno è più lungo dell'autobus. - The train is longer than the bus.

When comparing two nouns using più ... di (more ... than), the word di combines with the definite article (the word for "the") of the second noun. Because "the bus" is l'autobus, di + l' combines to form dell'.

Why does the translation say "longer" instead of "more long"?

In English, we often add "-er" to short adjectives (like turning "long" into "longer"). Italian doesn't have an "-er" ending. You always use più (more) followed by the adjective. So, più lungo translates to "longer", but literally means "more long".

Does the word lungo change if we compare feminine things instead?

Yes! Lungo is an adjective, so it must agree with the first noun in the comparison (the thing being described). Since il treno is masculine and singular, we use lungo. If we were talking about a car (la macchina), which is feminine, it would be più lunga.

Why is it l'autobus and not il autobus?

Autobus is a masculine noun that starts with a vowel. In Italian, masculine singular words starting with a vowel take l' instead of il to make pronunciation smoother.