Benign: Describing a growth that is confined to a specific site within a tissue and gives no evidence of invading adjacent tissue (Weinberg, 2007). Benign tumors are typically not life threatening.

Biomarker: A characteristic that is objectively measured and evaluated as an indicator of normal biological processes, pathogenic processes, or pharmacologic responses to an intervention (IOM, 2010).

Body mass index (BMI): A measure of adiposity calculated from an individual’s height and weight as an alternative for direct measures of body fat (CDC, 2011).

BRCA1/BRCA2: Human genes that belong to a class of genes known as tumor suppressors. Mutation of these genes has been linked to hereditary breast and ovarian cancers (NCI, 2011).

Carcinogen: An agent that contributes to the formation of a tumor (Weinberg, 2007).

Case–control study: A type of observational analytic study. Enrollment into the study is based on presence (“case”) or absence (“control”) of disease. Characteristics such as previous exposure are then compared between cases and controls (CDC, 2010).

Chromatin: Complex of DNA, histones, and non-histone proteins found in the nucleus of a eukaryotic cell. The material of which chromosomes are made (Alberts et al., 2002).

Circadian rhythm: Physical, mental and behavioral changes that follow a roughly 24-hour cycle, responding primarily to light and darkness in an organism’s environment (NIGMS, 2011).

Cluster: An aggregation of cases of a disease or other health-related condition, particularly cancer and birth defects, which are closely grouped in time and place. The number of cases may or may not exceed the expected number; frequently the expected number is not known (CDC, 2010).

Cohort: A well-defined group of people who are followed up for the incidence of new diseases or events, as in a cohort or prospective study. A group of people born during a particular period or year is called a birth cohort (CDC, 2010).

Confidence interval: A range of values for a statistic of interest, such as a rate, constructed so that this range has a specified probability of including the true value of the variable. The specified probability is called the confidence level, and the endpoints of the confidence interval are called the confidence limits (CDC, 2010). It may be thought of as the range of values that are consistent at a given level of confidence with a quantitative observation or measurement.

Confidence limit: The minimum or maximum value of a confidence interval (CDC, 2010).

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