The comitative case is one that Tolkien abandoned in his later writings. Indeed, the function of this case is not entirely clear, though its name implies that it indicates an “accompanying” noun. In its first appearance, the comitative case used the suffix -iko (PE16/113), and in this form it may have appeared in some sentences from the earliest drafts of the Markirya poem, as suggested by the editors of PE16 (Gilson, Smith, Wynne, Hostetter and Welden):

• ᴱQ. ar tanda kiryaiko lúte [or lunte] (PE16/56, 57, 60).

This sentence is unglossed, but may have meant “and with that ship sailed”.

Conceptual Development: There was no comitative case in the Early Qenya Grammar (EQG), and its first appearance was in some declension charts later in the 1920s (PE16/113-5), where it had the singular form -iko (kiryaiko), dissimilated to -ito after velars (telkoito). It had a dual form -uhto and plural forms -linko/-inko after vowels and consonants respectively. An identical set of singular/dual suffixes -iko/-uhto appear in the Entu, Ensi, Enta Declension; this declension is unlabeled so it is not certain that these are actual comitative inflections, but it seems very likely given that they are in complete agreement with the declensions on PE16/113-5.

The comitative was omitted from Tolkien’s lengthy discussion on the Declension of Nouns from the early 1930s, but reappeared in some charts from later in the 1930s, with singular/dual/plural endings -l/-lte/-líle and a new short plural form -ile (PE21/42-43). It kept this basic form in later charts, but Tolkien declared it was an archaic (OQ.) inflection (PE21/47, 50). This version of the suffix may be related to the preposition ᴱQ. le “with (accompaniment)” (QL/52).

The last published form of the comitative was the singular/dual/plural endings -ko/-uko/-iko in a chart probably composed in the late 1930s or early 1940s (PE21/53-55).

The full set of conceptual developments is given in the table below, using the version numbers for the declension charts from PE16 and PE21; the Entu, Ensi, Enta Declension (EEED) is inserted before version 3 as discussed in the entry on noun cases. Sh. Pl. = “Short Plural” are for shorter plural forms where they exist.

V	Comitatives	Sg.	Du.	Pl.	Sh. Pl.
EEED	vocalic	-iko	-uhto
EEED	consonantal	-iko	-uhto
3	vocalic	-iko	-uhto	-linko
3	vocalic	-iko	-uhto	-inko
5a	vocalic	-l	-lte	-líle	-ile
5b	vocalic	-l	-lte	-il/-líle	-l/-ile
5c	vocalic	-l	-lte	-lil/-líle	-il(e)
6	vocalic	-ko	-uko	-iko

Neo-Quenya: I recommend against using the comitative in Neo-Quenya. Its function can be replaced by the preposition ó “with”.