Not that it matters, mostly, but I do want to get the words right. So we are reading a book on someone who is mixed Native American Ojibwe and white.
Some people in my class, let’s say, are Indian (from India) and white. We agreed that would be mixed, but for example, someone who is English and Swedish would not be because they are just white.
Would they not be mixed race, mixed ethnicity, or be neither?


What we refer to as ‘races’ are racialised groups of people.
source
So it’s the society you live in that defines what groups of people get racialised and who belongs to that group. In the US and Europe, racialised groups include Arabs, African descended black and brown people, Eastern Asian people, Southern Asian people, latinx people, Native Americans, Roma/Sinti people, etc.
Since racialisation is purely a social construct, the people who get racialised change over time. Italians used to be a racialised group in the US but are now considered ‘white’.
With white, people usually refer to the ‘in-group’ of a society (from a US and European perspective). Being white means that you are not racialised. The answer to the question if someone would be considered ‘mixed’ if they descend from both England and Swedish is usually no, because English and Swedish people are considered white and don’t face characterisation or discrimination based on how they look.
Racialisation is unscientific and a form of discrimination. It’s a fact in society and it’s important to be aware that some people get racialised and thus treated differently based on their appearance, but trying to characterise people in a set of ‘races’ is not scientific because it is purely based on something as subjective as appearance.