See the Picture

You learned "on = 〜の上に". So you say "on the table" — fine. But then you see "on Monday". On… top of Monday? It makes no sense. You memorized a Japanese word, not the real thing. The problem is the method, not you.

Each one carries ONE picture

A preposition is not a list of translations. Each one carries one picture — one shape of space. Hold the picture, and you never need the list.

Here are the three big ones. On is touching a surface. The cup touches the top of the table — on. In is inside a boundary, inside a space. The key sits inside the bag — in. At is a single point. You stand at one spot, the door — at.

The same picture stretches to time

Now the magic. The picture does not stay in space. It stretches to time, with the same shape.

On the table → on Monday. A day is a flat surface you put things on. You touch that one day. In the box → in May. A month is a wide space, a boundary around many days. You are inside it. At the door → at five o'clock. A clock time is a single point, sharp and small. You meet right there.

And it does not stop at time. In trouble, in love — a state is a space you are inside. Same picture again. Once you see it, you stop guessing.

Stop translating, start seeing

So forget "on = 〜の上に". When you reach for a preposition, do not search for the Japanese word. See the shape. Is it a point? Say at. A surface? Say on. A space you are inside? Say in. The picture chooses for you.