Although an infant's color vision is not as sensitive as an adult's, it is generally believed that babies have good color vision by five months of age. Most babies start crawling at about 8 months old, which helps further develop eye-hand-foot-body coordination.
A language tree, or family tree with languages substituted for real family members, has the form of a node-link diagram of a logical tree structure. Such a diagram contains branch points, or nodes, from which the daughter languages descend by different links.
In languages with tagged unions such as ML, a tree node is often a tagged union of two types of nodes, one of which is a 3-tuple of data, left child, and right child, and the other of which is a leaf node, which contains no data and functions much like the null value in a language with pointers.