The rim is flat and there is a rather deep well, or cavetto.

边是平坦，有一个相当深底部，或称为圆底。

This paper introduces a simple semimicro-distillation apparatus,In this apparstus,a three-necked flask is used as steam generator.

文介绍一种用三颈圆底烧瓶作为蒸汽发生微量水汽蒸馏装置。