The Oils and Plants Aromatherapy Glossary gives definitions of Aromatherapy and Herbal Terms.

Here are the results for the letter t

Tannins

any of a class of yellowish or brownish solid compounds found in many plants and used as tanning agents, mordants, medical astringents, etc. Tannins are derivatives of gallic acid with the approximate formula C76H52O46 Also called tannic acid

Terpeneless Oil

Essential oils from which the monoterpene hydrocarbons have been removed.

Terpenoid

Essential oil constituents based on the isoprene skeleton, but containing a functional group.

Tincture

Solutions obtained by maceration of natural raw materials in ethanol. Such products are commonly used in herbal medicine.

Tonic

Strengthens and improves bodily performance.

Triglycerides

A naturally occurring ester of three fatty acids and glycerol that is the chief constituent of fats and oils.