'Ton-class' (dūn jí) is a compound noun used primarily in technical, industrial, and transportation contexts to classify the size or capacity of vehicles, vessels, or equipment by weight—specifically in metric tons. The first character 吨 (dūn) means 'ton' (metric ton, 1,000 kg), while 级 (jí) means 'class', 'grade', or 'level'. Together, they form a measurement-based classification term—not a literal count of tons, but a category indicating scale or magnitude.

This term appears frequently in descriptions of ships (e.g., '5,000-ton-class frigate'), aircraft ('200-ton-class cargo plane'), or even large machinery. It’s not used for everyday objects or people, and it’s rarely seen outside engineering, maritime, aviation, or logistics domains. Unlike simple numerals, 吨级 functions as a fixed lexical unit meaning 'in the X-ton range' or 'of X-ton scale', often paired with numbers or modifiers like '大型' (large-scale) or '超' (super).