Riccio vs. arricciato

The Italian words 'riccio' and 'arricciato' both refer to curly hair, but they have subtle differences in usage and connotation.

Riccio

'Riccio' is an adjective that describes naturally curly or wavy hair. It refers to hair that is inherently curly without any artificial styling.
Maria ha i capelli ricci.
(Maria has curly hair.)
Il suo bambino è nato con i capelli ricci.
(Her baby was born with curly hair.)

Arricciato

'Arricciato' is the past participle of the verb 'arricciare' (to curl) and describes hair that has been artificially curled or styled to be curly.
Per la festa, Giulia si è arricciata i capelli.
(For the party, Giulia curled her hair.)
I capelli arricciati di Paolo sono il risultato di un trattamento permanente.
(Paolo's curled hair is the result of a perm treatment.)

Summary

While 'riccio' refers to naturally curly hair, 'arricciato' describes hair that has been styled or treated to become curly. 'Riccio' is typically used for inherent hair texture, whereas 'arricciato' implies a temporary or artificial state of curliness.