#nav- vb. "judge" (cited in the form navë, apparently the 3rd person aorist). Also given with pronominal suffixes: navin *"I judge" (Tolkien's free translation: "I think"), navilwë "we judge" (VT42:33, 4, VT48:11)
Quenya
nam-
verb. to judge, to judge, *think (have as an opinion)
nav-
judge
nav-
verb. to judge, think [have as an opinion]
Námo
judge
Námo (1) noun "Judge", name of a Vala, normally called Mandos, properly the place where he dwells (WJ:402)
ham-
judge
#ham- (2) vb. "judge", attested in the aorist form hamil "you judge". (VT42:33; notice the pronominal ending -l "you". See nemë. The verb #ham- with the meaning "judge" may seem to be an ephemeral form in Tolkien's conception.)
ham-
verb. to judge
nam-
judge
#nam- vb. "judge", attested in the 1st person aorist: namin "I judge" (VT41:13). Compare Námo.
nem-
judge
[#nem- vb. "judge", attested as endingless aorist nemë, changed by Tolkien to hamë and finally to navë "in all but one case" (Bill Welden). Forms like námo "judge" and namna "statute" point rather to #nam- (q.v.) as a verb "to judge" (VT42:34); the verb namin "I judge" is even listed in Etym.]
nem-
verb. to judge
námo
noun. judge
The verb nam- “judge” appeared in 1968 notes associated with The Shibboleth of Fëanor, attested in the phrase namin alasaila “I judge [it] unwise” (VT41/13). This version of the verb is consistent with the name Námo, given in The Silmarillion as the true name of Mandos (S/28).
In a marginal note within Late Notes on Verb Structure (LVS) from 1969 Tolkien revised the root to √NDAB “to judge” with a new form Návo to replace Námo (PE22/154 note #53). These notes initially had nem- for “judge”, revised to ham- and finally to nav- (PE22/154 note #53, 55, 56); it was after all these revisions that he coined the new root √NDAB.
The verb nav- “judge” appeared in several phrases:
la năvin karitalya(s) mára “I do not advise you to do so, (lit.) I don't judge your doing (it) good”
lá karitas, navin, alasaila ná “not doing this would be (I think) unwise”
alasaila ná lá kare tai mo nave mára “it is unwise not to do what one judges good”
Based on the above phrases, it seems the basic sense of the verb is “judge” or “think = ✱have as an opinion”.
Conceptual Development: Tolkien introduced the name Námo in the 1950s, which is probably where this concept originated. It seems to have remained √NAM up through 1968, and then nam- >> nem- >> ham- >> nav- in 1969.
Neo-Quenya: For purposes of Neo-Quenya, I prefer to use the form nam- “judge, ✱think [have as an opinion]” for consistency with the name Námo in The Silmarillion as published.