Red hair in the context of "Erik the Red"

White Americans (sometimes also called Caucasian Americans) are Americans who identify as white people. In a more official sense, the United States Census Bureau, which collects demographic data on Americans, defines "white" as "[a] person having origins in any of the original peoples of Europe, the Middle East, or North Africa". Individuals within this group have light skin tones and hair colors that include brown, blonde, black or red. White Americans have historically constituted the majority population in the United States, though their share has been gradually declining in recent decades. As of the latest American Community Survey conducted by the U.S. Census Bureau in 2024, an estimated 59.8% of the U.S. population—approximately 203.3 million people—identify as White alone, while Non-Hispanic Whites account for 56.3% of the population, or roughly 191.4 million people. Overall, 72.1% of Americans identify as White either alone or in combination with one or more other racial groups. European Americans are by far the largest panethnic group of white Americans and have constituted the majority population of the United States since the nation's founding. Middle Eastern Americans constitute a much smaller demographic of white Americans, making up around 1.1% of the US population in 2020.

According to the 2020 census, 61.6% of Americans, or 204,277,273 people, identified as White alone. This represented a national decrease from a 72.4% white alone share of the US population in the 2010 census. The share of Americans identifying as White alone or in combination (including multiracial white people) was 71.0% in 2020, a smaller decline from 74.8% of the population in 2010. As opposed to the declines seen in the white alone population, the number of people identifying as part white (in combination with other races) saw a large increase, growing from 2.4% of the population in 2010, to 9.4% in 2020.

The Dharmaguptaka (Sanskrit: धर्मगुप्तक; Chinese: 法藏部; pinyin: Fǎzàng Bù; Vietnamese: Pháp Tạng bộ) is one of the eighteen or twenty early Buddhist schools, depending on the source. They are said to have originated from another sect, the Mahīśāsakas. The Dharmaguptakas had a prominent role in early Central Asian and Chinese Buddhism, and their Prātimokṣa (monastic rules for bhikṣus and bhikṣuṇīs) are still in effect in East Asian countries to this day, including China, Vietnam, Korea, and Japan as well as the Philippines. They are one of three surviving Vinaya lineages, along with that of the Theravāda and the Mūlasarvāstivāda.

Epistasis is a phenomenon in genetics in which the effect of a gene mutation is dependent on the presence or absence of mutations in one or more other genes, respectively termed modifier genes. In other words, the effect of the mutation is dependent on the genetic background in which it appears. Epistatic mutations therefore have different effects on their own than when they occur together. Originally, the term epistasis specifically meant that the effect of a gene variant is masked by that of a different gene.

The concept of epistasis originated in genetics in 1907 but is now used in biochemistry, computational biology and evolutionary biology. The phenomenon arises due to interactions, either between genes (such as mutations also being needed in regulators of gene expression) or within them (multiple mutations being needed before the gene loses function), leading to non-linear effects. Epistasis has a great influence on the shape of evolutionary landscapes, which leads to profound consequences for evolution and for the evolvability of phenotypic traits.

Auburn hair is a human hair color, a variety of red hair, most commonly described as reddish-brown in color. Auburn hair ranges in shades from medium to dark. It can be found with a wide array of skin tones and eye colors. The chemical pigments that cause the coloration of auburn hair are often pheomelanin with high levels of eumelanin.