Newick format is a parenthesized notation for rooted trees or unrooted trees, especially phylogenetic trees. Sibling subtrees are separated by commas, the children of an internal graph vertex are enclosed in parentheses, and a semicolon terminates the tree. For example,
 |
represents a binary tree with the two pairs of leaves 
and 
.
Labels can follow closing parentheses, and a branch length can follow a label after a colon. Thus Newick format can store both the topology of a tree and numerical information on its edges. Different orders of sibling subtrees encode the same tree, since Newick format does not assign an order to siblings. An unrooted tree has no distinguished root vertex; its rootedness is independent of the order in which its subtrees are written.
