The gentilic noun are adjectives that determine the place of origin of people or things.
As adjectives have gender (masculine or feminine) and number (singular or plural).
REGULAR SPANISH EXAMPLES
Castilla = castellano; Soria = soriano; Sevilla = sevillano.
Álava = alavés; Gijón = gijonés; Barcelona = barcelonés; León = leonés.
Castellón = castellonense; Melilla = melillense; Almería = almeriense.
Extremadura = extremeño; Madrid = madrileño; Albacete = albaceteño.
Alicante = alicantino; Bilbao = bilbaíno; Salamanca = salmantino.
IRREGULAR SPANISH EXAMPLES
Ávila = abulense; Badajoz = pacense; Huelva = onubense.
Huesca = oscense; Fuerteventura = majorero; Elche = ilicitano.
Betanzos = brigantino; Cabra = egabrense; Calahorra = calagurritano.
Calatayud = bilbilitano; Martos = tuccitano; Orihuela = orcelitano.