Glossary
Plain-language definitions of scientific terms used across the site. Terms with a dotted underline show definitions on hover.
Study Types
meta-analysisA study that combines results from multiple independent studies to draw stronger conclusions. Considered the highest level of evidence.
systematic reviewA comprehensive summary of all available research on a specific question, using strict methods to find and evaluate studies.
RCTRandomized Controlled Trial. Participants are randomly assigned to a treatment or placebo group, considered the gold standard for testing interventions.
cohort studyA study that follows a group of people over time to see how certain factors affect health outcomes.
placeboAn inactive treatment (like a sugar pill) given to a control group for comparison with the real intervention.
double-blindA study design where neither participants nor researchers know who receives the treatment or placebo, reducing bias.
Statistics
sample sizeThe number of participants in a study. Larger sample sizes generally produce more reliable results.
p-valueA measure of how likely the results occurred by chance. Below 0.05 is generally considered statistically significant.
effect sizeHow large the measured impact of an intervention is. A statistically significant result can still have a small, practically meaningless effect.
confidence intervalA range of values that likely contains the true effect. Narrower intervals mean more precise estimates.
statistical significanceA result unlikely to have occurred by chance alone (typically p < 0.05). Does not necessarily mean the effect is large or clinically meaningful.
Biology & Neuroscience
bioavailabilityThe proportion of a substance that enters your bloodstream and can have an active effect. Higher bioavailability means more of what you take is actually used by your body.
half-lifeThe time it takes for half of a substance to be eliminated from your body. Determines how long an effect lasts and how often you need to take it.
GABAGamma-aminobutyric acid. The brain's main inhibitory neurotransmitter. Promotes calm, relaxation, and sleep.
dopamineA neurotransmitter involved in motivation, reward, focus, and pleasure. Many supplements and habits affect dopamine levels.
serotoninA neurotransmitter that regulates mood, sleep, and appetite. Low serotonin is associated with depression and anxiety.
cortisolThe primary stress hormone. Healthy levels follow a daily rhythm (high in morning, low at night). Chronic elevation is harmful.
melatoninA hormone produced by the pineal gland that signals your body it's time to sleep. Suppressed by bright light at night.
circadian rhythmYour internal 24-hour biological clock that regulates sleep, hormones, body temperature, and metabolism.
adenosineA molecule that builds up during wakefulness and creates sleep pressure. Caffeine works by blocking adenosine receptors.
NAD+Nicotinamide adenine dinucleotide. A coenzyme essential for cellular energy production. Levels decline with age.
autophagyThe process by which cells clean up and recycle damaged components. Activated by fasting, exercise, and certain compounds.
mitochondriaThe energy-producing structures inside cells. Mitochondrial health is linked to aging, energy levels, and chronic disease.
neuroplasticityThe brain's ability to form new neural connections and reorganize itself. Can be enhanced by learning, exercise, and certain supplements.
HPA axisHypothalamic-pituitary-adrenal axis. The body's central stress response system that controls cortisol release.
inflammationThe immune system's response to injury or threat. Acute inflammation is protective; chronic inflammation drives many diseases.
oxidative stressAn imbalance between free radicals and antioxidants in the body, contributing to cell damage and aging.
gut-brain axisThe bidirectional communication system between the gut microbiome and the brain, affecting mood, cognition, and immune function.
microbiomeThe community of trillions of bacteria and other microorganisms living in your digestive tract. Affects immunity, mood, and metabolism.
Supplement Terms
adaptogenA natural substance that helps the body adapt to stress and maintain balance. Examples: ashwagandha, rhodiola.
nootropicA substance that enhances cognitive function, memory, or focus. Can be natural (lion's mane) or synthetic.
chelatedA mineral bound to an amino acid for better absorption. Chelated magnesium (like glycinate) absorbs better than oxide.
senolyticA compound that selectively removes damaged, aging (senescent) cells. Studied for anti-aging potential.
hormesisA biological response where a small dose of stress (cold, heat, exercise) triggers beneficial adaptations.
Health Metrics
PSQIPittsburgh Sleep Quality Index. A standardized questionnaire used in research to measure sleep quality. Lower scores mean better sleep.
VO2 maxMaximum oxygen uptake during exercise. One of the strongest predictors of longevity and cardiovascular health.
HRVHeart Rate Variability. The variation in time between heartbeats. Higher HRV generally indicates better cardiovascular fitness and stress resilience.
BMIBody Mass Index. A simple ratio of weight to height. Useful at population level but doesn't distinguish muscle from fat.