Clone

Nonterminals that have exactly the same definitions, are only cluttering the grammar, and can be painlessly united.

Related smells: Foldable

Reference

Mats Stijlaart and Vadim Zaytsev. 2017. Towards a taxonomy of grammar smells. In Proceedings of the 10th ACM SIGPLAN International Conference on Software Language Engineering (SLE 2017). ACM, New York, NY, USA, 43-54.