Dual systems means the use of both inch-pound and metric systems. For example, an item is designed, produced and described in inch-pound values with soft metric values also shown for information or comparison purposes.

Hybrid systems means the use of both inch-pound and standard metric values in specifications, standards, supplies, and services; e.g., an engine with internal parts in metric dimensions and external fittings or attachments in inch-pound dimensions.

Metric system means the International System of Units established by the General Conference of Weights and Measures in 1960.

Soft metric means the result of mathematical conversion of inch-pound measurements to metric equivalents in specifications, standards, supplies, and services. The physical dimensions are not changed.