vertical:

解析: vertical 指与平面、水平线成 90 度角的，也可指沿此方向上升或下降的。

例句: What does the vertical axis of that graph represent?

翻译: 那个图的纵轴代表什么？

例句: They used to go to a gorge lined with vertical cliffs.

翻译: 他们以前常去一个峭壁林立的峡谷。

例句: There was a vertical drop to the ocean.

翻译: 至海洋有一段垂直落差。

erect:

解析: erect 强调笔直挺拔的，而不是倾斜、弯曲或倒塌的。

例句: A waiter stood erect beside their table.

翻译: 他挺直地坐在课桌后。

例句: Stand with your arms by your side and your head erect.

翻译: 手放两边，昂首站立。

例句: Her head was erect and her back was straight.

翻译: 她抬头挺胸。

upright:

解析: upright 指站或坐得笔直的，也指处于竖直方向的。

例句: If you have to carry this bottle of paint with you, then you‘d better keep it upright.

翻译: 如果你非要带着这瓶颜料的话，你最让它保持直立。

例句: Gradually raise your body into an upright position.

翻译: 慢慢起身，呈直立状态。

例句: Helen sat upright in her chair.

翻译: 海伦笔直地坐在椅子上。