This post skips as small bridging entry.
Sindarin and Noldorin have a set of “impersonal” verbs that do not have an explicit subject. The best example of this is the Noldorin verbs eil “it is raining” and bui “I must, *(lit.) it needs”, the latter explicitly marked as impersonal. Another probable impersonal verb is S. gor- “warn, urge”, which used impersonally means “to feel an urge”. Comparing these to Quenya syntax, in all likelihood these impersonal verbs put the purported subject into the dative, as in bui annin mened “it needs for me to go = I must go” or gôr annin mened “it urges me to go = I feel an urge to go”.
English handles such impersonal constructions by using “it” as a placeholder subject as in “it rains”. In Quenya impersonal verbs have no subject, as in mauya “it compels = I must” vs. mauyas “he/she compels”. The picture is murkier in Sindarin, however. Unlike Quenya, the Sindarin 3rd person singular verb form has no subject suffix, so mên = “he/she/it goes”, vs. menin “I go”. This makes an “impersonal” construction indistinguishable from a 3rd. sg. pronominal subject in Sindarin.
In Quenya, impersonal verbs are one of the primary ways of expressing passive voice. A passive expression in Quenya uses an impersonal verb form such as Q. nahtane i atan “[it] slew the man = the man was slain”. In Sindarin, however, S. annanc i adan could mean “it slew the man” or “he/she slew the man”; there is no such ambiguity in Quenya, since “he/she slew” = nahtanes. The net result is that Sindarin probably does not use uninflected impersonal verbs as extensively for passive voice constructions as Quenya does. There is, however, at least one example of the 3rd. pl. suffix -r being used in a passive construction:
- S. i sennui Panthael estathar aen “who should be called Fullwise” (referring to Samwise, SD/129).
Here estathar = “they will call” seems to be used in a passive construction in much the same way that English uses constructions like “they say ...”. Thus i sennui Panthael estathar aen is more literally “who they should call Fullwise”, where “they” is unspecific and therefore generic.
In English, the true passive voice is formed using the past/passive participle, as in “the man is slain”. It is possible that Sindarin can likewise use the passive participle for passive voice constructions; such systems have been proposed in Thorsten Renk’s Pedin Edhellen: a Sindarin-Course (PESC/133) and in Fiona Jalling’s A Fan’s Guide to Neo-Sindarin (FGNS/97-102). This is also one tentative of such a construction in Tolkien’s own writing:
- S. mae g(ī)’ovannen “well (art) thou met” (PE17/17).
This Sindarin example must be taken with a grain of salt, since Tolkien used it as a tentative explanation for the welcoming phrase mae govannen, and he ultimately decided on a different explanation. However, it seems to indicate that a passive participle can be used very much like in English for passive constructions, so that perhaps i adan dangen = “the man (is) slain”.
One complication is that Sindarin has no copula (“to be” verb) in such expressions, so the “is” from English is unexpressed in Sindarin. This could make it tricky to distinguish “the man is slain” from “the man was slain” or “the man will be slain”. Most Neo-Sindarin writers assume there is no past or future markers in Sindarin “to be” expressions, and the verb tense must be deduced from context. I personally suggest that Sindarin might use explicit past or future copulas: ᴺS. nî- “was” and tho- “will be”, as in i adan nî nangen “the man was slain (dangen, nd-)” or i adan tho nangen “the man will be slain”. This is, however, speculation on my part and is not the normal Neo-Sindarin practice.