:Nuclear Stress Rule:

Often abbreviated to NSR. One of the rules proposed by Chomsky & Halle in The sound pattern of English which account for prominence relations in words and phrases. The input to the rule is a string of bracketed items with primary lexical stress already marked (by the Main Stress Rule). The NSR re-assigns primary stress to the rightmost primary stressed syllable in a phrasal component and reduces all other stresses by one degree in that component. The rule starts working on the most deeply embedded component first. After it has applied, the brackets surrounding the relevant component are erased and the rule applies again to then next deeply embedded component.

Chomsky N. & Halle M. (1968) The sound pattern of English. New York: Harper & Row.