It obviously depends on country you come from. Here is what CIC says about surname:
What do you mean by surname?
Your surname is your family name. It is sometimes called your “last name.” If your name is spelled differently on your official documents, please write your name as shown in your passport. When filling out applications, type your surname as it appears on your passport, travel or identity document or any letters you got from the visa office or case processing centre where you sent your application (even if the name is misspelled). Do not use initials.
If you do not have a family name on your passport, travel or identity document, enter all your given name(s) in the surname field and leave the given name field blank. Do not enter “*”, “Not applicable” or “NA”.