Why don't we say: "The shop is opened"? [duplicate]

Let's consider both examples:

The shop is closed.

The shop is open.

In this case, "open" and "closed" are adjectives. The word "closed" is an example of a participial adjective. It is similar to others such as "surprised", "intrigued", and "tired". These adjectives usually come from words with Latin roots. Other adjectives, such as "open" and "bright", have Germanic roots and do not take English forms requiring "ed" at the end.

Hope this helps!

"Open" and "Closed" are both adjectives describing the shop.

It's just one of those situations where a verb matches the adjectives one way but not for its opposite. You wouldn't say "the shop is close," since the adjective close has a completely different definition.