On the proposed redefinition of the mole

This letter calls for reconsidering the new definition of the mole, which has been proposed in the draft chapter 2 for the SI Brochure, posted on the BIPM website. It is argued that the list of particles should be deleted from the new definition of the mole. The necessary elements of the definition are summarized and another wording is suggested. Proposals to rename ?amount of substance? are briefly discussed.