Race refers to physical traits only.
I assume that this question is meant to have you be able to distinguish between race and ethnicity. These are words that are often used interchangeably by the general public, but which mean very different things to social scientists.
I would fill in this blank by saying “Race refers to a group of physical characteristics that are believed to separate people into different groups.” There are two aspects to this answer that we must pay attention to. First, we must note that race is used to refer to physical characteristics. We determine what race a person is simply by looking at them. We look at the color of their skin and hair. We look at the shape of their eyes and their noses. We look at the texture of their hair. All of this is visible at a glance. This is in contrast to ethnicity. Ethnicity refers to culture. We cannot tell a person’s ethnicity by looking at them. A person who is of Hispanic ethnicity may look very similar to a person who is ethnically American or ethnically Filipino. Ethnicity can only be determined by talking to a person or by observing their customs, not simply by looking at their physical appearance.
The second aspect of this answer is that these characteristics “are believed to” differentiate groups of people. Social scientists know that race is a socially constructed concept. There is no biological way to define races and to say that they are different from one another.
Thus, I would answer this question by saying “Race refers to a group of physical characteristics that are believed to separate people into different groups.”
Race refers to a way to group people together primarily based on physical appearance. Those physical traits, such as eye/hair color, size, skull shape, and other measurable physical attributes are inherited from their ancestors and are considered genetic traits.
The idea of race seems to mainly be a 19th and 20th century concept and is losing currency among sociologists, biologists, and others. What we think of as racial characteristics today may not be nearly as ancient and ingrained as is commonly believed, and racial characteristics can change over a relatively short period of time.
The increase in "mixed race" children and families is another factor in making race a less useful grouping, if it ever was one. Many sociologists believe that race has done little other than divide people and isn't something which fits into academic studies of humanity.
This previous question on the same topic contains some more in-depth discussion.
Race is one of the major divisions of mankind. It refers to having distinct physical characteristics. It is a group or set of people with common features.