A branch (, UK also ), sometimes called a ramus in botany, is a woody structural member connected to but not part of the central trunk of a tree (or sometimes a shrub). Large branches are known as boughs and small branches are known as twigs. The term twig often refers to a terminus, while bough refers only to branches coming directly from the trunk. Due to a broad range of species of trees, branches and twigs can be found in many different shapes and sizes. While branches can be nearly horizontal, vertical, or diagonal, the majority of trees have upwardly diagonal branches. A number of mathematical properties are associated with tree branchings, they are natural examples of fractal patterns in nature, and, as observed by Leonardo da Vinci, their cross-sectional areas closely follow the da Vinci branching rule. Words Because of the enormous quantity of branches in the world, there are a variety of names in English alone for them. In general however, unspecific words for a branch (such as rise) have been replaced by the word branch itself. = Specific terms =A bough can also be called a limb or arm, and though these are arguably metaphors, both are widely accepted synonyms for bough. A crotch or fork is an area where a trunk splits into two or more boughs. A twig is frequently referred to as a sprig as well, especially when it has been plucked.