pol- (1) vb. "can" = have physical power and ability, as in polin quetë "I can speak (because mouth and tongue are free)". Cf. ista-, lerta- as verbs "can" with somewhat different shades of meaning. (VT41:6, PE17:181)
Quenya
pol-
verb. can, to be (physically) able to
pol-
can
lerta-
can
lerta- vb. "can" in the sense "be free to do", being under no restraint (physical or other). Lertan quetë "I can speak (because I am free to do so, there being no obstacle of promise, secrecy, or duty)". Where the absence of a physical restraint is considered, this verb can be used in much the same sense as pol- (VT41:6)
A verb in notes associated with the 1959-60 essay Ósanwe-kenta meaning “can, have physical power and ability” (VT41/6). The example Tolkien gave was polin quetë “I can speak (because mouth and tongue are free)”, as opposed to istan quetë “I can speak (because I have learned a language)” [= “I know (how) to speak”] and lertan quetë “I can speak (because I am free to do so there being no obstacle of promise, secrecy, duty)”. Another later expression for “can” was the verb ec- “may, can, have chance, opportunity or permission”, which was used impersonally: ecë nin care sa “I can do that, (lit.) there is a chance for me to do that” (VT49/20).
Conceptual Development: The English-Qenya Dictionary of the 1920s had the verb ᴱQ. mala- “am able to (used of capacity, ability)” (PE15/67). The first version of Quenya Personal Pronouns (QPP1) from the late 1940s had ᴹQ. valya “can” (PE23/74), probably related to the root ᴹ√BAL having to do with power (Ety/BAL). Quendian & Common Eldarin Verbal Structure (EVS1) and Quenya Verbal System (QVS) from this same period had ᴹQ. kav- “can”, with past tense kambe “could” (PE22/92, 102), derived from the root ᴹ√KAB “be able, capable” (PE22/105, 127).
Neo-Quenya: For purposes of Neo-Quenya, I think it is possible all of the 1950s and 60s words for “can” co-exist with slightly different meaning: pol- referring to physical ability, ista- to mental ability, lerta- to lack of social limits, and ec- to chance and opportunity. I wouldn’t use any of the words from the 1940s or earlier, though.