Righthand head rule

In generative morphology, the righthand head rule specifies that the rightmost morpheme in a morphological structure is always the head. What this means is that it is the righthand element that provides the primary syntactic information. For instance, the word 'person' is a noun, but if the suffix '-al' is added and 'personal' is derived. 'Personal' is an adjective, and the righthand head rule holds that the PoS information is provided by the suffix '-al', which is the righthand element. The projection of syntactic information from the righthand element onto the derived word is known as feature percolation.