Trichomes (from the Greek τρίχωμα - trichomic tri·chom'ic (trĭ-kŏm'ĭk, -kō'mĭk, trī-) adj.
meaning "growth of hair"), are fine outgrowths or appendages on plants and certain protists. These are of diverse structure and function.

A common type of trichome is a hair. Plant hairs may be unicellular or multicellular, branched or unbranched. Multicellular hairs may have one or several layers of cells. Branched hairs can be dendritic (tree-like), tufted, or stellate (star-shaped).,

A common type of trichome is the scale or peltate hair: a plate or shield-shaped cluster of cells attached directly to the surface or borne on a stalk of some kind.

Any of the various types of hairs may be glandular.
In describing the surface appearance of plant organs, such as stems and leaves, many terms are used in reference to the presence, form, and appearance of trichomes. The most basic terms used are glabrous—lacking hairs— and pubescent—having hairs. 
    * glabrous, glabrate – lacking hairs or trichomes; surface smooth
    * hirsute – coarsely hairy
    * hispid – having bristly hairs
    * downy – having an almost wool-like covering of long hairs
    * pilose – pubescent with long, straight, soft, spreading or erect hairs
    * puberulent – minutely pubescent; having fine, short, usually curly, hairs
    * pubescent – bearing hairs or trichomes of any type
    * strigillose – minutely strigose
    * strigose – having straight hairs all pointing in more or less the same direction as along a margin or    midrib
    * villosulous – minutely villous
    * villous – having long, soft hairs, often curved, but not matted
(related; THC, Cannabis, Hash)