← Learn Health & fitness terms for beginners
The Modern Health Dictionary Search essential language from measurements, GLP-1 and peptide science, nutrition, weight loss, resistance training and muscle. Expand “Why this matters” to see the practical distinction and continue to the relevant tool or guide.
Search health terms Measurements & concentrations Units, solutions and the distinctions between amount, concentration, dose, strength and potency.
MassThe amount of matter in a substance or object, commonly expressed as kg, g, mg or mcg (µg).
WeightScientifically, the force gravity exerts on an object. In everyday health discussions, “weight” usually means body mass.
VolumeThe three-dimensional space occupied by a substance, commonly expressed as litres (L) or millilitres (mL).
ConcentrationHow much of a specified constituent is present relative to a stated amount of a mixture or solution. Mass concentration is mass divided by volume.
StrengthThe amount of active substance contained in or delivered by a product. It may be a total amount or a concentration, depending on the product.
DoseThe quantity of a substance administered at one time or over a defined period.
Dosage regimenThe broader instructions for use, including dose, frequency, timing and duration.
PotencyThe amount or concentration required to produce a defined biological effect. Potency is not concentration or strength.
DilutionDecreasing a solution’s concentration, usually by adding solvent.
ReconstitutionAdding a specified liquid to a dry or concentrated product to prepare a solution or suspension.
SoluteThe substance being dissolved.
SolventThe liquid or other medium in which a solute is dissolved.
SolutionA homogeneous mixture containing one or more solutes in a solvent.
DiluentA substance or liquid used to dilute or reconstitute a preparation.
Final volumeThe total volume after all components have been combined.
Total amountThe complete quantity of a substance present, such as 10 mg.
AliquotA measured portion taken from a larger sample.
Unit (U or IU)A product-specific measurement of biological activity used for certain substances.
DensityMass divided by volume.
Specific gravityThe ratio of a substance’s density to the density of a specified reference substance.
SolubilityHow much of a substance can dissolve under specified conditions, including solvent and temperature.
ViscosityA fluid’s resistance to flow.
GLP-1 & peptide science The language used in medicine labels, clinical trials and receptor science.
Active ingredientThe substance responsible for a product’s intended biological or pharmacological activity.
ExcipientA formulation ingredient other than the active ingredient.
PeptideA chain of amino acids that can act as a biological signal or form part of a larger protein.
ReceptorA cellular target that recognizes particular signalling molecules and can trigger a biological response.
AgonistA substance that activates a receptor and produces a biological response.
AntagonistA substance that binds to a receptor and blocks or reduces its activation.
Half-lifeThe time required for an amount or concentration in the body to decrease by approximately half during a specified elimination phase.
BioavailabilityThe fraction of an administered dose that reaches systemic circulation, with consideration of how quickly it becomes available.
Pharmacokinetics (PK)What the body does to a drug: absorption, distribution, metabolism and elimination.
Pharmacodynamics (PD)What a drug does to the body, including the relationship between exposure and biological response.
TitrationPlanned adjustment of a dose over time according to a defined regimen or clinical response.
Steady stateDuring repeated dosing, the condition in which the average rate entering the body equals the average rate eliminated.
EfficacyThe maximum effect a substance can produce under defined conditions.
InvestigationalBeing studied but not approved for routine clinical use for the stated purpose.
Adverse effectAn unwanted or harmful effect associated with an intervention.
ContraindicationA circumstance in which a treatment should not be used because the potential risk is unacceptable.
Drug interactionWhen another drug, supplement, food or factor changes a drug’s effects or exposure.
Nutrition & weight loss Energy, nutrients and body-composition terms used throughout the site.
Calorie (kcal)The food-energy unit commonly called a calorie on nutrition labels; one kcal equals 1,000 small-calories.
BMR / RMREstimates of energy used at rest. Basal metabolic rate uses stricter measurement conditions than resting metabolic rate.
TDEETotal daily energy expenditure: resting needs plus movement, exercise and the thermic effect of food.
Energy balanceThe relationship between energy consumed and energy expended over time.
Calorie deficitA period in which energy intake is lower than energy expenditure.
MacronutrientA nutrient needed in relatively large amounts: protein, carbohydrate and fat.
MicronutrientA vitamin or mineral needed in smaller amounts for normal function.
Dietary fibreCarbohydrate components that resist digestion in the small intestine and have varied physiological effects.
Lean massBody mass that is not fat mass; it includes muscle, water, organs, bone and other tissues.
Body-fat percentageEstimated fat mass expressed as a percentage of total body mass.
Resistance training & muscle The beginner vocabulary needed to understand programmes and preserve muscle.
Resistance trainingExercise in which muscles work against an external resistance.
HypertrophyAn increase in the size of muscle fibres and overall muscle tissue.
Muscle protein synthesisThe biological process of building new muscle proteins.
Progressive overloadGradually increasing the training challenge as capacity improves.
Set and repetitionA repetition is one complete exercise cycle; a set is a group of repetitions performed together.
Training volumeA measure of work performed, often described using hard sets, repetitions or load × repetitions.
IntensityDepending on context, either load relative to maximum strength or the effort required by a set.
RIRRepetitions in reserve: an estimate of how many technically sound repetitions remained at the end of a set.
RPERating of perceived exertion: a scale describing how hard an effort felt.
Training to failureContinuing a set until another repetition cannot be completed with acceptable technique.
1RMThe greatest load that can be lifted once with acceptable technique for a specific exercise.
RecoveryRestoration and adaptation between training sessions, influenced by sleep, nutrition, stress and programme demands.
SarcopeniaAge-related loss of muscle strength, quantity and physical performance assessed using clinical criteria.
