Rheumatoid arthritis An autoimmune disease that causes chronic inflammation of the joints.

Rickets A disorder caused by a deficiency of vitamin D, calcium, or phosphate, which leads to softening and weakening of the bones and is seen most commonly in children 6 to 24 months of age.

Sarcoidosis A disease that results from a specific type of inflammation of tissues of the body that can appear in almost any body organ, often starting in the lungs or lymph nodes.

Scleroderma A pathological thickening and hardening of the skin caused by swelling and thickening of fibrous tissue.

Systemic lupus erythematosus A chronic, autoimmune, inflammatory disease of connective tissue that causes fever, weakness, fatigue, joint pains, and skin lesions on the face, neck, or arms.

Tachysterol An isomer of ergosterol that forms vitamin D₂ when irradiated with ultraviolet light.

Tolerable Upper Intake Level The highest average daily nutrient intake level that is likely to pose no risk of adverse effects to almost all individuals in the general population. As intake increases above the Tolerable Upper Intake Level, the potential risk of adverse effects may increase.

Transgenic Having genetic material (deoxyribonucleic acid) from another species.

Tuberculosis A highly contagious infection caused by the bacterium called Mycobacterium tuberculosis.

Ultraviolet Pertaining to electromagnetic radiation having wavelengths in the range of approximately 5 to 400 nm; shorter than visible light, but longer than X-rays.

Ultraviolet B Medium wavelength (280 to 320 nm) ultraviolet rays from the sun; help synthesis of vitamin D₃; the “burning” rays in the ultraviolet spectrum.