More often than not, the terms “surname”, “last name”, and “family name” are interchangeable in  the English-speaking world. “Surname” is sometimes considered more formal than “family name”.  The “last name” is different from “surname” and “family name” in parts of the world where the  family name is written first.

Between “surname” and “family name”, the only difference nowadays seems to be that “surname” is more  often used in formal documents, while “family name” is a less formal term.

It is, however, possible for the two to be different in rare cases, such as:

Leonardo da Vinci

Here, “da Vinci” is not Leonardo’s family name, but it is his surname. His surname shows where he’s from,  as “da Vinci” means “from Vinci”. These cases were more common in the past.

In other parts of the world, however, the last name may be different from the surname and family name. For  example, in countries that speak Chinese, the surname or the family name is usually written first. In these  cases, using the term “last name” could cause confusion. Thus, it is better to avoid it and use either  “surname” or “family name” in these situations.

The term “surname” refers to the name a person shares with other members of his or her family,  tribe, or community.

A surname is what identifies an individual as a member of a family, tribe, or community. It is usually  synonymous with the term “family name”, however, it is possible for the two to be different.

Where the surname is located differs from culture to culture. There are even some cultures that do not make  use of surnames.

In many places, including English-speaking cultures, names are written as follows: [first name/given name]  + [surname/family name]. In these cases, surnames are also last names.

Below, in bold, are examples of surnames that are also last names:

John Doe

John F. Kennedy

Clark Joseph Kent

Juan de la Cruz

Linda Flynn-Fletcher

There are also many places in which surnames are not written after the first name. They are written as  follows: [surname/family name] + [given name].

Below, in bold, are examples of surnames that are not last names:

Kim Yuna

Hua Mulan

Lim Eunsoo

The term “last name” refers to the name that is written at the end of one’s name. 

The “last name” is what identifies an individual as a member of a family, tribe, or community in places  where names are written as follows: [first name/given name] + [last name]. In the English-speaking world,  the term “last name” is synonymous with the terms “surname” and “family name”.

Below, in bold, are examples of what a “last name” is:

Joe Bloggs

Harry James Potter

Lily Evans

Bruce Wayne

Anthony Stark 

The term “family name” refers to the name that identifies a person as a member of a particular  family. 

The “family name” is what identifies a person as a member of a particular family. It can be interchangeable  with the terms “surname” and “last name”, but only to the extent that these identify a person as a member of  a family.

Examples of what a “family name” is can be seen below, in bold:

Gomez Addams 

Morticia Addams 

Wednesday Addams 

Pugsley Addams 

Here, it can be assumed that all of these people are members of the Addams family.

In the United Kingdom, data shows that “surname” is the most popularly used among “surname”,  “last name”, and “family name”. 

Google Ngram Viewer charts how often certain words are used in a wide range of books. According to data  from books that use British English that were published between the years 1900-2019, the term “surname” is  the most popular among the three. It has also remained the most popular since the year 1900, by a wide  margin.