Why do we say “open” and “closed”? Why is one in present tense and the other in past tense?

Question

Edit: to clarify, I mean when shops have a sign that says “open” versus “closed”. Why is it not “opened/closed” or “open/close”?

In: Other

Answer 1

In English you can make adjectives out of the past participle of verbs. “Closed” is one such example, but also “hidden”, “sold out”, “renovated”, etc. Consequently, you can do the same with “opened” in theory, but it is not often used in practice (“The recently opened store” is an example where you cannot use “open”).

However, “open” is actually originally an adjective, and is cognate to adjectives in the other Germanic languages.

In fact, the adjective form “close” used to also exist in English (from wiktionary I found 1830, Thomas Thomson (chemist), The History of Chemistry, volume 1, pages 30–31:
As the alchymists were assiduous workmen—as they mixed all the metals, salts, &c… and subjected such mixtures to the action of heat in close vessels) likely under influence from the French word clos/close which is a past participle in French.

Summary:

Past participles may be used as adjectives. “Open” was originally a Germanic adjective which is now a verb. “Close” was originally a Latinate past participle which is now a verb. Nowadays, only “open” survives as an adjective, although “close” was also an adjective once.