美国传统大学词典将“种族”定义为“种族特征，背景或隶属关系”。字典定义了种族的根词 – “种族” – 是一个“相当大的群体，共享一个共同的，独特的种族，民族，宗教另一方面，“种族”这个词的意思是“当地的地理或全球人口群体，根据遗传物理特征区分为或多或少的群体。”因此，种族更多地是社会学的描述。文化虽然种族主要被认为植根于科学。然而，美国遗产指出种族的概念“从科学的角度来看是有问题的。”该词典指出：“今天描述的种族的生物学基础不是在可观察的物理特征中，而是在线粒体DNA和Y染色体的研究中。早期体质人类学家概述的分组很少与基因水平的研究结果一致。“ 换句话说，很难在白人，黑人和亚洲“种族”成员之间进行生物学上的区分。科学家们将种族视为一种社会建构。但是一些社会学家也认为种族是一种社会建构。社会学家罗伯特·耶瑟说：“社会学家认为种族和种族是社会建构，因为它们不是植根于生物学上的差异，它们会随着时间的推移而发生变化，而且它们从来没有坚定的界限。”例如，美国的白度观念已经扩大。意大利人，爱尔兰人和东欧移民并不总是被认为是白人。在21世纪初，这些群体被归类为属于白人“种族”。种族群体的想法也可以扩大或缩小。虽然意大利裔美国人被认为是美国的一个民族，但一些意大利人认为其地区起源比其国家更多。他们认为自己不是意大利人，而是认为自己是西西里人。 “非裔美国人”是另一个有问题的民族类别。这个词通常适用于美国的任何黑人，许多人认为它指的是前奴隶的后代，他们参与了这个群体的文化传统。但是，从尼日利亚到美国的黑人移民可能会与这些非洲裔美国人实行完全不同的习俗，并认为这个词并不能定义他。 “种族可以显示或隐藏，取决于个人喜好，而种族身份总是在展示，”他说。印度裔美国女性可以通过穿着纱丽，束缚和指甲花手艺来展示她的种族，或者穿着西装来隐藏它。同一个女人几乎无法掩饰指出她是南亚血统的身体特征。通常情况下，只有多种族人才具有使他们的祖先起源静音的特征。像一些意大利人一样，许多尼日利亚人不认同他们的国籍，但他们的团体在尼日利亚 – 伊博，约鲁巴，富拉尼等。虽然种族和种族可能是社会结构，但Wonser认为他们在不同方面有所不同。
The American Heritage College Dictionary defines “ethnicity” as one’s “ethnic character, background or affiliation.” The dictionary defines the root word of ethnicity—“ethnic”—as a “sizable group of people sharing a common and distinctive racial, national, religious, linguistic or cultural heritage.” The word “race,” on the other hand, means “a local geographic or global human population distinguished as a more or less distinct group by genetically transmitted physical characteristics.” So ethnicity is more of a sociological description of culture, while race is largely thought to be rooted in science. However, American Heritage points out that the concept of race is problematic “from a scientific point of view.” The dictionary notes: “The biological basis for race is described today not in observable physical features but in the study of mitochondrial DNA and Y chromosomes, and the groupings outlined by earlier physical anthropologists seldom coincide with findings at the genetic level.” In other words, it’s difficult to make biological distinctions between members of white, black, and Asian “races.” Scientists widely view race as a social construct. But some sociologists view ethnicity as a social construct, too. Sociologist Robert Wonser says, “Sociologists see race and ethnicity as social constructions because they are not rooted in biological differences, they change over time, and they never have firm boundaries.” The idea of whiteness in the United States has expanded, for example. Italians, Irish, and Eastern European immigrants were not always thought of as white. In the early 21st century, these groups are categorized as belonging to the white “race.” The idea of an ethnic group can also be broadened or narrowed. While Italian-Americans are thought of as an ethnic group in the United States, some Italians identify more with their regional origins than their national ones. Rather than view themselves as Italians, they consider themselves Sicilian, for example. “African-American” is another problematic ethnic category. The term is often applied to any black person in the U.S., and many assume it refers to the descendants of former slaves who partake in cultural traditions of this group. But a black immigrant to the U.S. from Nigeria may practice completely different customs from these African-Americans and believe the term doesn’t define him. “Ethnicity can be displayed or hidden, depending on individual preferences, while racial identities are always on display,” he says. An Indian-American woman may display her ethnicity by wearing a sari, bindi, and henna hand art or conceal it by wearing Western dress. The same woman can do little to conceal the physical characteristics that point out she’s of South Asian ancestry. Typically, only multiracial people have traits that mute their ancestral origins. Like some Italians, many Nigerians don’t identify with their nationality but with their group in Nigeria—Igbo, Yoruba, Fulani, etc. While race and ethnicity may be social constructs, Wonser argues that they differ in distinct ways.