便函
an informal letter sent by an organization
便步走, 辩才, 变成, 便池, 变丑, 便当, 便道, 遍地开花, 变电站, 变调, 变动, 变法, 变法儿, 便饭, 变分法, 便服, 变革, 变更, 变工, 变故, 变黑, 变红, 变厚, 便壶, 辩护, 变化, 变幻, 变换, 变换设备, 遍及, 变价, 便笺, 变焦距镜头, 变节, 辩解, 便览, 便利, 变脸, 变量, 变流器,
