介词 If something moves onto or is put onto an object or surface, it is then on that object or surface. 到…之上

I took my bags inside, lowered myself onto the bed and switched on the TV.

我把我的包拿进去，坐到了床上，打开了电视。

介词 You can sometimes use onto to mention the place or area that someone moves into. 移向 (某处)

The players jogged onto the field.

运动员们慢慢跑进赛场。

At exactly 6:00 p.m., Marcia drove onto the motorway.

下午6点整，马西娅开车上了高速公路。

介词 You can use onto to introduce the place toward which a light or someone's look is directed. (光线或视线) 朝向

...the metal part of the door onto which the sun had been shining.

…阳光一直照耀着的门的金属部分。

The colours rotated around on a disc and were reflected onto the wall behind.

那些色彩在一张圆盘上旋转，并被反射到后面的墙上。

介词 If a door or room opens onto a place, that place is directly in front of it. (门或房间) 对着…

The door opened onto a well-lit hallway.

这扇门对着一个照明很好的门厅。

介词 When you change the position of your body, you use onto to introduce the part your body which is now supporting you. (身体重心) 移向

As he stepped backwards she fell onto her knees, then onto her face.

他往后退步时，她双膝跪倒在地，接着脸也着地。

Puffing a little, Mabel shifted her weight onto her feet.

梅布尔有些气喘,将她身体的重量移到了双脚上。

介词 When you get onto a bus, train, or plane, you enter it in order to travel somewhere. 登上 (交通工具)

As he got on to the plane, he asked me how I was feeling.

他上飞机时问我感觉如何。

介词 Onto is used after verbs such as "hold," "hang," and "cling" to indicate what someone is holding firmly or where something is being held firmly. 用于(hold)，(hang)，(cling)等动词之后，表示某人紧握或某物被紧握

The reflector is held onto the sides of the spacecraft with a frame.

反光器被一个框紧紧地固定在宇宙飞船的各个侧面。

介词 If people who are talking get onto a different subject, they begin talking about it. 转向 (新的话题)

Let's get on to more important matters.

咱们谈些更重要的事吧。

介词 You can sometimes use onto to indicate that something or someone becomes included as a part of a list or system. 成为…的一部分

The Macedonian question had failed to get on to the agenda.

马其顿问题没能提到议事日程上来。

The pill itself has changed a lot since it first came onto the market.

自从投放市场以来，这种片剂本身已经改变了许多。

介词 If someone is onto something, they are about to discover something important. 将要发现

He leaned across the table and whispered to me, "I'm really onto something."

他隔着桌子探过身悄悄地跟我说，“我真的要有重大发现了。”

介词 If someone is onto you, they have discovered that you are doing something illegal or wrong. (对某人做的坏事) 已经明白了

I had told people what he had been doing, so now the police were onto him.

我已经告诉人们他一直在从事的勾当，所以现在警察都对他很清楚了。

映射到…上

在上

在…之上；对…了解；映射到…上

upon / up

映射的；自身的；映成的

inhouse