tengwa (pl. tengwar is attested) (1) noun "letter" Tengwa (ñ) is defined as "any one visible sign representing (theoretically) any one audible teñgwe" (phoneme) (VT39:17). In non-technical usage tengwa was equivalent to "consonant", since only the consonants were full signs (WJ:396, TEK). In the Etymologies, tengwa was apparently emended from tengwë (VT46:17).
Quenya
tengwa
noun. sign
tengwa
letter
tanwa
sign, token
tanwa noun "sign, token" (Tolkien marked this word with a query, but it is not clearly rejected). Also tanna (#1). (PE17:186)
sarat
letter
sarat (pl. sarati given) noun "letter", any individual significant mark, used of the letters of Rúmil after the invention of Fëanor's tengwar (WJ:396). Cf. sarmë.
narwë
sign, token
[narwë (and short nar, unless this is an incomplete form) noun "sign, token"] (VT45:37)
tanna
sign, token
tanna (1) noun "sign, token" (MR:385, PE17:186), also tanwa (PE17:186)
taina
sign
#taina (2) noun "sign", isolated from Tainacolli *"Sign-bearer" MR:385
tana-
to show, indicate
tana- (2) vb. "to show, indicate" (MR:350, 385, 471) (cf. the demonstrative tana "that")
sign, indicator, letter