本文件是关于公制应用的主要美国国家标准。它强调使用国际单位制（SI），这是国际公认的现代公制。它包括有关国际单位制的信息、国际单位制认可使用的有限单位清单、换算系数清单，以及有关风格和用法的一般指南。它还列出了更老的a？metrica？不再使用的装置。primary一词意味着美国的其他度量标准应与本文件一致。

This document is the primary American National Standard on application of the metric system. It emphasizes use of the International System of Units (SI), which is the modern, internationally accepted metric system. It includes information on SI, a limited list of units recognized for use with SI, and a list of conversion factors, together with general guidance on style and usage. It also lists older "metric" units that shall no longer be used. The word primary implies that other metric standards in the United States should be consistent with this document.