Learn Italian: Ognuno è diverso. - Everyone is different.

Just like "everyone" or "everybody" in English, ognuno is grammatically singular. It focuses on every individual as a single unit, so it always takes a third-person singular verb like è.

Could I use ciascuno here instead of ognuno?

Yes! You could absolutely say Ciascuno è diverso. They are completely interchangeable in this context. Ognuno is just slightly more common in everyday conversation when talking about people in general, while ciascuno sometimes emphasizes "each individual one" a little more.

If "everyone" includes women, why does the adjective end in -o (diverso)?

When making a general statement about a mixed group of people, Italian grammar defaults to the masculine singular form. However, if you were talking exclusively about a group of women (like "each of the sisters"), you would change both the pronoun and the adjective to feminine: ognuna è diversa.

What is the difference between saying Ognuno è diverso and Tutti sono diversi?

They mean essentially the same thing, just like "Everyone is different" and "All are different" in English. The grammatical difference is that ognuno is singular and focuses on the individuals, while tutti means "all" and is plural, requiring a plural verb and a plural adjective.