A nationality behaves like an adjective, so it agrees with the person it describes: -o for a man, -a for a woman, plus -s in the plural. Ones ending in a consonant add -a for the feminine (español / española). They are written in lower case, unlike English.
Examples
- Soy italiano, de Roma.
- I'm Italian, from Rome.
- Ella es española y yo soy mexicano.
- She is Spanish and I am Mexican.
- Somos alemanes.
- We are German.
The mistake to avoid
Country names keep their capital (España) but nationalities lose it (español).
Where this fits in
Greetings & introductions, Spanish A1: Say hello, give your name, ask someone else's, and where they're from.