zài / jǐ / hé / tú / xíng / zhōng / tū / xiàn / tōng / cháng / yòng / yú / biǎo / shì / wài / bù / biān / jiè

在几何图形中，凸线通常用于表示外部边界。

In geometric figures, convex curves are often used to represent outer boundaries.