So one of the really wild things about the Swedish language is that it has not one, not two, but *three* types of passive voice, and it exploits passive constructions to the hilt. https://twitter.com/asayeed/status/1296810316026781698

Just for example, English officially has one form of passive voice, made with "to be".

"After the faculty had their fill, the leftover pizza was eaten by the hungry students."

German has *two* passive voices, Vorgangspassiv (process passive), made with "werden" (to become), and Zustandspassiv (status passive), made with "sein" (to be).

The difference is in the name, process passives are about something in the process of being changed.

Status passives have already had the change applied to the object. This is more or less the distinction. In English, the work for process passives is roughly done by continuous aspect. ("The pizza *was being eaten* by the students.")

Swedish not only has the German distinction (process passives with "bli" -- "become"; status passives with "vara" -- "be") but also has an additional "s-passive" formed by adding an s to the verb (and/or supplanting the final "r" in the present tense for most verbs).

The s-passive can be used to substitute for the "bli" process passive and typically is in spoken Swedish. But, it has a couple of additional functions.

For one thing, Swedish (and Danish and Norwegian, I think) has "accidentally" resurrected the Indo-European mediopassive via the s-passive. It has also permitted the development of Latin-style deponent verbs.

Swedish for "See you later" is often "Vi ses igen", literally "We see-passive again", ie, it's a reciprocal mediopassive equivalent to saying "We'll see each other later".

German has a more direct equivalent but only via a reflexive, which German uses reciprocally "Wir sehen uns wieder." (aka "Auf *Wieder**sehen*")

English uses neither a reciprocal mediopassive (mostly doesn't exist) nor reflexives (English has them but somewhat deprecated). English has gone all in on reciprocal pronominal expressions ("We'll see *each other* again".)

Swedish and German have these ("varandra" and "einander" respectively) but are not nearly as prolific with them as English.

The other function of the Swedish s-passive is deponent. For example, the verb for "breathe" -- "anda" -- is used strictly deponently with an s-passive. "Han andas tyst." ("He's breathing quietly.")

But there's more! Deponent verbs can be used transitively in Swedish despite the s-passive form. !!!

"Han andas ut gasen." -- "He breathes out the gas."

Since every verb form can be s-passivized and they can have mediopassive interpretations (reflexive, reciprocal, or simple ordinary process passive) you get *all kinds* of highly economical constructions in Swedish, ...

... which is one of the things that makes Swedish one of the few European languages that requires shorter explanation plaques in museums than English.

Another thing Swedish does with its s-passives is eliminate the need for a second perfective auxiliary (to form the composite past tense of Western European languages).

Most Western European languages require some verbs to be put in past tense with "to have" and some with "to be", corresponding roughly to "unaccusativity" that also drives the Latin phenomenon of deponent verbs.

English is the one language I know of that barrels through and simply ignores this distinction, using "to have" only and forgetting unaccusativity. For example, "She has bought a guitar" vs "She has gone to the store". In French and German, you'd need "to be" for the latter.