Triquetrous (triqueter). Three-edged (with 3 salient angles).
Truncate (truncatus). Terminating abruptly as though cut off at the end.
Tube (tubus). A hollow, more or less elongated body, especially the lower undivided and more or less narrowed part of the perianth, or a concave receptacle bearing the perianth at the margin.
Tuber (tuber). A short and thick, more or less fleshy underground part of a stem, not surrounded by scales, or a similar root.
Tubercle (tuberculum). A wart-like swelling on the surface of an organ.
Umbel (umbella). A centripetal (racemose) inflorescence with a very short axis and stalked flowers arising apparently all from the same point.
Umbonate (umbonatus). Bearing a boss in the centre of the surface.
Unarmed (inermis). Without spines or bristles.
Undershrub (suffrutex). A plant woody in the lower part of the above-ground stem, herbaceous towards the top.
Unifoliolate (unfoliolatus). With a single leaflet, which is jointed to the leaf-stalk.