plurale tantum

  RobertHaigh  —  Grammar Tips
 A NOUN which is invariably plural in form, even though it may be singular in sense. Examples include oats, cattle, remains, pants, scissors, binoculars, pyjamas, shorts and tweezers. Such nouns are awkward to count: we cannot say *a pants or * a cattle, and we must say instead a pair of pants and a head of cattle. The plural of plurale tantum is pluralia tantum.