Such problems are too much a matter of proportion, balance, symmetry, pattern congruence, and the like - features closely allied to one's esthetic feeling. It is for this reason that different linguists describe the same structure somewhat differently.
- Nida (1948), Pag. 427

Any science of classification becomes involved in the same difficulty. Thus, taxonomists in the fields of botany and zoology are faced with the same problem of determining the degree and the nature of structural likeness or difference which are to be regarded as significant in establishing classes and subclasses.
- Nida (1948), Pag. 427