Terms Starting with "X"

39 terms

x

x a letter used to symbolize a variable of interest. For example, in a regression equation, x may represent a particular predictor or independent variable. x′ symbol for x prime.

X̄ (X bar)

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X chromosome

X chromosome the sex chromosome that is responsible for determining femaleness in humans and other mammals. The body cells of normal females possess two X chromosomes (XX), whereas males have one X chromosome and one Y chromosome (XY). In humans, various authorities estimate that the X chromosome carries between 1,000 and 2,000 genes, including many responsible for hereditary diseases (see sex-linked). Abnormal numbers of X chromosomes lead to genetic imbalance and a range of disorders and syndromes. See also fragile X syndrome.

x prime

x prime (symbol: x′) the predicted or expected value of a given variable of interest, x.

x-axis

x -axis n. the horizontal axis on a graph. See abscissa.

x-coordinate

x -coordinate n. the horizontal value in a pair of graph coordinates (x, y), which indicates how far to move left or right from the origin along the x-axis. For example, in the ordered pair (4, 8), the x-coordinate is 4 and the corresponding vertical y-coordinate value is 8. See Cartesian coordinate system.

x-intercept

x -intercept n. in an equation representing a straight-line relationship between two variables, the value of variable x when the value of variable y equals zero. For example, in the general linear equation format x = a + by, a represents the x-intercept.

X-linked

X-linked adj. see sex-linked.

X-ray

X-ray n. an electromagnetic emission of short wavelength produced by bombarding a heavy metal target, such as tungsten, with high-energy electrons in a vacuum tube. X-rays are used for diagnostic purposes to visualize internal body structures: The radiation can penetrate most substances and produce images of objects on photographic film (see radiography) or can cause certain chemicals to fluoresce. Prolonged or unnecessary exposure can be extremely damaging; therefore, when X-rays are used therapeutically for diagnosis or to destroy malignant cells (see radiation therapy), great precautions are taken to limit and target exposure. Also called roentgen ray.

x′

x a letter used to symbolize a variable of interest. For example, in a regression equation, x may represent a particular predictor or independent variable. x′ symbol for x prime.

Xanax

Xanax n. a trade name for alprazolam.

xanthine

xanthine n. see methylxanthine.

xantho- (xanth-)

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xanthocyanopsia

xanthocyanopsia n. a form of color blindness in which red and green are not perceived and objects are thus seen in shades of yellow or blue.

xanthomatosis

xanthomatosis n. any of several disorders marked by an accumulation of excess lipids, such as cholesterol, in the body due to a metabolic disturbance. This accumulation leads to the formation of foam cells in skin lesions and other symptoms. These disorders include bulbi xanthomatosis, marked by fatty degeneration of the cornea; Wolman’s disease; hypercholesterolemic xanthomatosis, or Type II hyperlipoproteinemia, associated with accelerated atherosclerosis and premature heart attacks; and normal cholesterolemic xanthomatosis (see Hand–Christian–Schüller syndrome). A related form of xanthomatosis results in cutaneous lesions and other effects in some people with diabetes.

xanthopsia

xanthopsia n. see chromatopsia.

xanthopsin

xanthopsin n. see visual yellow.

Xenazine

Xenazine n. a U.S. trade name for tetrabenazine.

xeno- (xen-)

Sorry, "xeno-xen" is not in the Dictionary of Psychology. Please report to APA if you believe this is an error.

xenoglossophilia

xenoglossophilia n. a tendency to use strange or foreign words, particularly in a pretentious manner.

xenoglossy

xenoglossy n. in parapsychology, the ostensible ability of a person to speak or write in a language that is entirely unknown to him or her.

xenophobia

xenophobia n. 1. a strong and irrational, sometimes pathological, fear of strangers. 2. hostile attitudes or aggressive behavior toward people of other nationalities, ethnic groups, regions, or neighborhoods. In nonhuman animals, xenophobia is manifested by territorial behavior (see territoriality) and is also seen in social groups where intruders are typically attacked and repelled. —xenophobic adj.

xenorexia

xenorexia n. the pathological ingestion of inedible objects.

xeroderma pigmentosum

xeroderma pigmentosum a syndrome acquired as an autosomal recessive trait (see recessive allele) and marked by extreme photosensitivity. It is caused by a defect in the ability of the body to repair damage to DNA resulting from exposure to ultraviolet light, which leads to cancerous changes in skin cells and increased mortality. Additionally, about 30% of people with this syndrome develop progressive neurological symptoms, including hearing loss, movement problems, loss of intellectual function, and seizures.

xerophthalmia

xerophthalmia n. excessive dryness of the eyes, due to histological changes in the cornea and conjunctiva. Xerophthalmia is a characteristic symptom of Sjögren’s syndrome, a systemic autoimmune disease with an onset between 40 and 65 years. Xerophthalmia is also one of the ocular effects of vitamin A deficiency.

XX

XX see sex chromosome.

XXX syndrome

XXX syndrome a rare disorder characterized by the presence of three X (female) chromosomes instead of the normal two X chromosomes (46,XX). The majority of affected females are physically and mentally normal. Delays in mental development, when present, are usually mild. Also called 47,XXX syndrome; triple-X condition; trisomy X.

XXXX syndrome

XXXX syndrome a disorder in which a female has four X chromosomes instead of the normal two X chromosomes (46,XX). Affected females are likely to have minor physical anomalies and mild developmental delays, but symptoms can also be moderate to severe. Also called 48,XXXX syndrome; tetrasomy X.

XXXXX syndrome

XXXXX syndrome a rare disorder in which a female has five X chromosomes instead of the normal two X chromosomes (46,XX). All affected individuals studied had intellectual disability, and some had ocular or other anomalies, such as patent ductus arteriosus (a heart defect), microcephaly, or limb abnormalities. Also called 49,XXXXX syndrome.

XXXXY syndrome

XXXXY syndrome a rare disorder in which a male inherits three extra X chromosomes in addition to the normal one X and one Y chromosome (46,XY). Affected individuals have a variety of anomalies, including abnormally small genitalia; a short, broad neck; and hypotonia (flaccid muscles). Most affected individuals have intellectual disability, impaired speech, and short stature. Also called 49,XXXXY syndrome.

XXXY syndrome

XXXY syndrome a relatively rare disorder in which a male inherits the full complement of both male and female sex chromosomes instead of either the normal two X chromosomes (46, XX) for females or the normal one X and one Y chromosome (46,XY) for males. Affected individuals have a normal penis but small testes and prostate, and about half develop enlarged breasts and have intellectual and developmental disabilities. Also called 48,XXXY syndrome.

XXY syndrome

XXY syndrome see Klinefelter’s syndrome.

XXYY syndrome

XXYY syndrome a disorder in which a male is born with a double complement of the normal XY chromosome pair (46, XY). Skeletal deformities, genital anomalies leading to infertility, enlarged breasts, and eunuchoid abdominal and hip fat are among the physical traits. Learning disabilities, especially reading problems, are common, along with delayed development of motor skills. Also called 48,XXYY syndrome.

XY

XY see sex chromosome.

xylene

xylene n. a volatile solvent that can cause kidney failure and death when chronically inhaled. See inhalant.

Xyrem

Xyrem n. a trade name for GHB.

XYY syndrome

XYY syndrome a chromosomal anomaly discovered in 1961 and initially believed to predispose males to aggression and violence. The theory was modified when XYY anomalies were found among normal males. Also called double-Y condition.

XYZ grouping

XYZ grouping a program in which school administrators assign students in the same grade to classes by virtue of their test scores and school records. Students with similar abilities are placed in “high,” “middle,” or “low” groups or classes; each group follows the same basic curriculum. Students in the middle and lower classes in XYZ programs do not increase their achievement as compared to students in traditional classes, but students in the higher classes in XYZ programs increase their achievement by about one month on a grade-equivalent scale as compared to students in traditional classes. In XYZ classes, self-esteem of lower ability students rises slightly and self-esteem of higher ability students drops slightly. See also ability grouping.

XYZ system

XYZ system a mathematically defined theoretical system for specifying colors in terms of three abstract primary colors, X, Y, and Z. The system was developed in 1931 by the International Commission on Illumination (CIE) and is often referred to as CIE XYZ color space.

Psychology Terms Starting With 'X'