A hierarchy is a set of objects all of which are connected by a relation that is asymmetric and transitive in the set.
Different kinds of hierarchies result depending both on the kind of object and the specific relation involved. The following is an open list of hierarchies that have some significance in linguistics. For each hierarchy, the constitutive relation is indicated. x is at a lower hierarchical level than y. In the last column, the kind of x and y is indicated.
| hierarchy | constitutive relation | kind of object |
|---|---|---|
| taxonomy | x is a y | concept |
| meronymy | x is part of y | thing |
| complexity hierarchy | y is more complex than x | concepts, things |
| abstractness hierarchy | y is more abstract than x | concepts |
| preference hierarchy | y is preferred to x | property |
| teleonomic hierarchy | x is a means to purpose y | processes/operations |
| implicational hierarchy | if x has a certain property, then y has that property | (propositions about) things |
| gradience | y has some property to a higher degree than x | (propositions about) things |