What do you call a member of royalty or nobility?

There is a whole raft of different modes of address to different grades of nobility - both for writing letters and speaking face-to-face.

When meeting the Queen, you address her as "Your Majesty" in your opening greeting (or reply), and then "Ma'am", pronounced either 'Mam' or 'Marm'.

For Prince Philip or Prince Charles, you would say "Your Royal Highness", and then "Sir".