Trichomes on plants are epidermal outgrowths of various kinds. The terms emergences or prickles refer to outgrowths that involve more than the epidermis.
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.