“Nominal: 1. Relating to nouns: a nominal group. 2. A noun or pronoun: He and bridge are the nominals in the sentence He crossed the bridge. 3. An adjective functioning as a noun: the poor (poor people); the accused (the accused person). The terms nominal group and nominal clause mean the same as noun phrase and noun clause. A nominal clause is a finite or non-finite clause that resembles a noun phrase in the range of its functions; for example, as the subjects of sentences, That he can’t lift his arm in That he can’t lift his arm worries me, and Smoking cigarettes in Smoking cigarettes can cause cancer.”
Excerpted from: McArthur, Tom. The Oxford Concise Companion to the English Language. New York: Oxford University Press, 2005.