A suffix appearing at the end of several words in the first draft of Lament of Akallabêth, variously glossed with different forms of the verb “to be”: burudan “heavy-is”, rōkhī-nam “bent-are”, īdōn “now is” (SD/312). Evidentally the suffix -n “is” is the singular form and -nam “are” is plural. The plural form probably includes the plural verbal suffix -m. This use of the suffix -n is probably no longer be valid in later versions of Adûnaic, as discussed below.
Carl Hostetter and Patrick Wynne suggested (VSH/36) that -nam maybe related to Q. ná- “to be”, but they fail to analyze the singular forms of the suffix. Andreas Moehn (LGtAG) does connect the singular instances of the suffix -n to the plural -nam, but without connecting it to Q. ná-. I think both authors got part of the story right: the suffixal form -na is mostly likely derived from the same Elvish root √NĀ as Q. ná-, losing its final a in the singular form but preserving it in the plural form when the plural suffix -m is added.
In its first two appearances in the draft version of the Lament, this suffix is attached to the predicate of a copula (a linguistic term for a “to be” expression). For that reason, the discussion here uses the term “predicate suffix” for this use of the -n suffix:
agannūlo burudan nēnum “death-shade heavy-is on-us” subject agannūlo “death-shade”, predicate buruda “heavy” + -n “is”.
īdō kathī batānī rōkhī-nam “lo! now all ways bent-are” subject batānī “ways”, predicate rōkhī “bent” + -nam “are”.
The suffix’s second two appearances in the draft version of the Lament are more ambiguous.
ēphalek īdōn akallabēth “far away lo!now is She-that-is-fallen”.
ēphal ēphalek īdōn athanātē “far far away is now the Land of Gift”.
Going by word order alone, it seems that the -n is attached to the predicate in both of these sentences as well. However, as Andreas Moehn points out (LGtAG), īdō could be the subject of both sentences if the predicates are the final word of each sentence, which is more consistent with the later subjective inflection.
In the later version of Adûnaic described in Lowdham’s Report, the suffix -n has a new function, namely as the common subjective suffix: -an/-n. This new use differs from the older one in that it applies to the subject of a copula instead of the predicate. Despite this grammatical change from draft-Adûnaic, the word form īdōn appears in all later versions of the Lament of Akallabêth except the final manuscript version.
Ēphalak īdōn Yōzāyan “far away now (is) Land of Gift” (SD/247).
Ēphal ēphalak īdōn hi-Akallabēth “far far away now (is) She-that-hath-fallen” (SD/247).
These later appearances of īdōn still have the gloss “now (is)”, so it seems possible that these they are remnants of the predicate suffix from draft Adûnaic. Moehn, Hostetter and Wynne all suggested (LGtAG, AAD/16) that these later appearances of īdōn can be reinterpreted as a subjective inflection. However, this interpretation is still problematic, since îdô would surely be a neuter instead of a common noun, whose subjective form would therefore be *îdôwa.
The suffix -n did not appear after īdō in the final manuscript version of the Lament, and the gloss “is” was removed as well:
Ēphalak īdō Yōzāyan “far away now Gift-land” (VT24/12).
Ēphal-ēphalak īdō hi Akallabēth “far far away now She that hath Fallen” (VT24/12).
It is my belief that Tolkien eventually decided that the suffix -n could no longer be used in this context and removed it.