Don, señor, Doña, y señora
What are the differences of these words : Don & señor. Doña & señora
Don Roberto, señor Alejandro, Doña María, señora Anita
Don - Doña are terms of respect.
Often my students call me Don Ian.
I am flattered but really prefer Don Juan.
"Don" seems to be something of a casual title, used with a person's first name. It lends a little more formality to a relationship than just the first name alone, but not to the level of "señor".
When I visited the eye doctor, she addressed me "Don Calvo". That was more formal than simply "Calvo" but less formal than "Señor Viejo."
The earlier answers are absolutely backwards. Don and Doña are terms of high respect awarded to meritorious persons, very similar to the titles Sir and Dame in British English. The criteria are a bit different but the usage is the same. Example: Elton John was knighted by the queen. Thereafter his official title became Sir Elton. The Spanish equivalents work similarly, always used with a first/given name, never a surname alone, just as we would not say Sir John in referencing Sir Elton John.
One other usage note. You will occasionally hear/see Don Nadie or Doña Nadie. That is a sarcastic term, meaning someone who thinks themselves to be important but are actually a nobody.