1. His soup spoon dropped onto the ground.
   他的湯勺掉到了地上。
2. A miner's lamp is fixed onto his helmet.
   礦燈固定在礦工的頭盔上。
3. I reached the gate that opened onto the lake.
   我走到臨湖而開的那扇門前。
4. He jumped onto the table.
   他跳上了桌子。

on.to

prep.（介詞）
On top of; to a position on; upon:
到…之上：在…頂端；在一位置上；在…上面：
例句：
The dog jumped onto the chair.See Usage Note at on
這條狗跳到了椅子上面參見 on

Informal Fully aware of; informed about:
【非正式用語】 知曉：非常熟悉；了解：
例句：
The police are onto the robbers` plans.
警察局都清楚搶劫犯的陰謀

adj.Mathematics （形容詞）【數(shù)學(xué)】
Of, relating to, or being a mapping such that every element of the set referred to is the image of an element in another.
映成的：一集合中的每一元素，經(jīng)映象后為另一集合至少一元素的象的；與之有關(guān)的；或成為象的