“ Thus the term “man” is concrete, while “manhood” and “humanity” are abstract, the names of the qualities implied. Confusions between abstract and concrete terms are frequent; thus the word “relation,” which is strictly an abstract term implying connexion between two things or persons, is often used instead of the correct term “relative” for people related to one another. Concrete terms are further subdivided as Singular, the names of things regarded as individuals, and General or Common, the names which a number of things bear in common in virtue of their possession of common characteristics. ”