Venetian is the proper adjective for Venice.
Roman is the proper adjective for Rome.
No, Franz is a proper noun (Frank or Francis are western versions of it). The names of people and places are generally proper nouns. A proper adjective is a word whose root is a proper noun-- like "Italy" is a proper noun, and Italian is a proper adjective: that new Italian restaurant is wonderful.
Yes, it is an adjective describing people or things in or from Italy. It can also refer to things associated with Italy's culture. The word Italian is also a demonym (noun) for a person in or from Italy (an Italian), or referring to the language Italian.
A common adjective describes a general characteristic of a noun, while a proper adjective is derived from a proper noun and specifically identifies a particular noun. For example, "blue" is a common adjective, while "Italian" is a proper adjective derived from the proper noun "Italy."
The correct spelling of the proper noun is Tucson, a city in Arizona. The similar word is the proper adjective Tuscan, referring to Tuscany in Italy.
The proper adjective for Portuguese is "Portuguese."
The proper adjective for southwest is "southwestern."
The proper adjective for Haiti is Haitian.
Vietnamese is the proper adjective for Vietnam.
The proper adjective for Siam is Siamese.
The proper adjective for Georgia is Georgian.