This paper attempts to present an over-all simplified picture of the principles and practice of stratigraphic classification and terminology with the objective of advancing general uniformity of usage.

Stratigraphic classification is the organization of the sequence of rock strata in the earth's crust into units under the various categories of classification provided by the many different attributes of these rocks. Stratigraphic terminology is concerned with the development of terms for these units.

If the concepts behind each classificatory category are clearly understood, a simple and effective terminology is readily achieved. Of particular importance is a clear distinction between the units of objective categories (those based directly on physical discernible of physically measurable rock features, such as lithology, fossil content, electrical properties, etc.) and the units of subjective categories (those derived indirectly from objective characters by inference or interpretation, such as units based on geologic age, environment of deposition, etc.) Equally important is the designation of type or reference sections for all kinds of stratigraphic units, without which they can not have any precise meaning.

The terminology of units and the relations between different categories of units are discussed and shown diagrammatically. Attention is called to specific cases of confusion resulting from lack of clear differentiation between objective and subjective categories and units. The particular importance of sound stratigraphic classification and terminology in petroleum geology is stressed. Verity, utility, and simplicity are recognized as principal features to be attained.