This is the most common Quenya word for “light”, derived from the root √KAL of similar meaning (RGEO/62; PE17/84). It appears in numerous compounds, either in its full form or in a reduced form cal-.
Conceptual Development: ᴱQ. kala appeared all the way back in the Qenya Lexicon of the 1910s glossed “daytime (sunlight), 12 hours” and derived from the early root ᴱ√KALA “shine golden” (QL/44), but it had the sense “light” in the phrase ᴱQ. i·kal’antúlien “Light hath returned” (LT1/184), and it was given as the cognate of G. gala “light, daylight” in the contemporaneous Gnomish Lexicon (GL/37).
ᴹQ. kala “light” appeared in The Etymologies of the 1930s as a derivative of the root ᴹ√KAL “shine” (Ety/KAL). Somewhat curiously in that document its primitive form was given as ᴹ✶k’lā́ (EtyAC/KAL), a form that also appeared in the first version of Tengwesta Qenderinwa (TQ1) from the 1930s (PE18/38). Tolkien may have used this variant form to explain N. glaw “radiance” (< ᴹ✶g’lā́), but in later writings S. glaw “sunshine” was derived from √LAW.
cala ("k")noun "light" (KAL). Concerning the "Qenya" verb cala-, see #cal- above.