An adjective suffix. When used with verbs, it functions like the English suffix “-able, -ible”: cénima “visible”, mátima “edible”, nótima “countable”. When used in this way, the base vowel of the verb is also lengthened, as opposed to when -ima is used as an ordinary adjective suffix without lengthening:
> Only the adjs. in -ima found with long stem vowel were adjs. of possibility. -ima was frequently used with stems (verbal, adj[ectival] or nominal) with a short vowel, and the sense possessing to a high degree (at all times and by nature) the property mention[ed]. So kalima “luminous (by nature always)”, vanima “beautiful”, norima “running, swiftly a course[?]”, kelima “fluent”, istima “wise (in sense of knowing much), knowledgeable, very well informed”, melima “loving, very affectionate” - but lamélima “unlovable” (PE22/156).
In most cases these two functions for the suffix -ima can be distinguished by the presense or absence of a long vowel, meaning “-able” (long vowel) or “having a [strong] nature of” (short vowel) respectively. But with many weak verbs (especially ta-causatives), lengthening was not possible and the a was retained, as with tultaima “✱fetchable, summonable” (PE22/156).
When used with intransitive verbs, the sense “-able” was not appropriate, so the suffix had its other meaning “having a (strong) nature of”:
> When formed from intransitive stems as kalima “luminous” [from the verb cal- “shine”] they differed from the [active] verbal participles in -ila (a) as being more intensive, (b) as being always aorist[?] and without special reference to a present or particular occasion (PE22/155).
Based on the example calima “luminous”, there was no vowel lengthening when the suffix was used with intransitive verbs.
Conceptual Development: As a general adjective suffix, ᴱQ. -ima dates all the way back to the Qenya Lexicon of the 1910s, but its first clear mention as a verbal suffix of possibility is in Qenya Verb Forms written in the 1920s where it was glossed “-able, possible”, including an example indicating it was associated with vowel-lengthening: tūlima (PE14/33).
In the Quenya Verbal System (QVS) of 1948 the suffix could use consonant-doubling as an alternate method of strengthening the stem: ᴹQ. mattima “edible” or ᴹQ. qettima “utterable” (PE22/111). In QVS it took the form -alima with weak verbs: ᴹQ. istalima “knowable” or ᴹQ. ortalima “able to be raised” (PE22/111). In Common Eldarin: Verb Structure (EVS2) of the early 1950s Tolkien said it sometimes took the form -tima, as in mastima < ✶matˢtimā (PE22/137). But elsewhere it was only used with vowel lengthening when functioning as a suffix of possibility.
Tolkien also discussed the -ima suffix at length in Late Notes on Verb Structure (LVS) written in 1969 (PE22/155-156), and the system in the main entry for using -ima is largely based on these 1969 notes. Based on the examples tultaima and lakaltaima from LVS, I believe weak verbs in Tolkien’s later system simply appended -ima to the verb stem. There is a somewhat confusing note in the margin of LVS that might contradict this:
> not ima, which when add[ed] to pre[sent?] stem had [?none] as in nútaila, nútaite, but nútima (PE22/156 and note #64).
This note might mean Tolkien changed his mind, and that -ima replaced the final vowel a in ta-causative núta- “lower”. However, the marginal note appears near a section on intransitive ta/ya-formative verbs, and I believe Tolkien temporarily confused himself, thinking núta- was ta-formative rather than ta-causative. Hat-tip to Lokyt who discussed this issue with me in Discord on 2024-06-01.
This does imply ta/ya-formatives like nahta- “slay” would replace their final a when combined with -ima, such as ✱nahtima “able to be slain”. However, since most such verbs are intransitive, they would rarely use the suffix -ima “able”.
-ima adjectival suffix. Sometimes it is used to derive simple adjectives, like vanima "fair" or calima "bright"; it can also take on the meaning "-able" (PE17:68), as in mátima "edible" (mat- "eat"), nótima "countable" (not- "count") and (with a negative prefix) úquétima "unspeakable" (from quet- "speak"). Note that the stem-vowel is normally lengthened in the derivatives where -ima means "-able", though this fails to occur in cenima "visible" (q.v., but contrast hraicénima, q.v.) and also before a consonant cluster as in úfantima "not concealable" (PE17:176). "X-ima" may mean "apt to X" (when the ending is added to an intransitive verbal stem), as in Fírimar "mortals", literally "those apt to die" (WJ:387). The adj. úfantima "not concealable" (PE17:176) also appears as úfantuma (PE17:180), indicating the existence of a variant ending -uma (possibly used to derive adjectives with a "bad" meaning; compare the ending *-unqua next to -inqua, q.v.)