There only two currently published questions in Sindarin (and none in its conceptual precursors): linnathol? “will you sing?” from 1969 (PE22/167) and man agorech? from the early 1950s (VT50/5), untranslated but almost certainly meaning “what have we done?” using the late-1940s, early-1950s 1st pl. inclusive pronominal suffix -ch (VT50/21-22). These two questions give us a fair amount of information, though.
The idea popped up on Vinye Lambengolmor that we could continue this fun project that we started on Google Plus but never finished.
We can discuss ideas here as we are progressing through the list (which is already quite advanced).
Here's the link to the spreadsheet:
Passive participles in Sindarin (and Noldorin) are reasonably well attested. For half-strong and derived verbs, its formation is straighforward: add -en to the past tense, with the final -nt become -nn- medially as usual. The clearest Sindarin example of this is the half-strong verb covad(a)- “(make) meet” with past tense covant, passive participle covannen “met” (PE17/16, 158).
In addition to tense, Sindarin verbs are also inflected with subject suffixes in the first and second person. The full set of suffixes (and their conceptual development) is discussed in the entry on subject suffixes. The treatment of 3rd person is somewhat unusual, however. The 3rd singular inflexion has no pronominal suffix, as in: agarfant beth “he spoke words” (PE17/126).
There is no future tense in Gnomish or Early Noldorin, perhaps because the Welsh present tense can also be used to describe the future: strictly speaking the Welsh “present tense” is really “non-past”, just like the English simple present. The first mention of a distinct future form is in Quendian & Common Eldarin Verbal Structure (EVS1) from the late 1940s: