A word appearing in notes from the late 1960s described as “light-substance” (NM/280), “light as an ethereal substance” (NM/283), or “liquid light” (NM/285), derived from the root √LIK “glide, slip, slide, drip” (NM/285). As Tolkien described it:
> Q. linque (n., adj.) “(bright/clear/gleaming) liquid”. This was applied (in Quenya) to dew (or to fine rain in sunshine); in Sindarin to pools or rills of clear clean water. It was probably in origin a “mythological” word - referring to the primitive Elvish conception of “light” as an actual substance (emitted by light-givers, but then independent), though ethereally fine and delicate (NM/285).
As such, it could apply to light itself envisioned as an insubstantial liquid or ethereal substance flowing through the air (photons), or other liquids glistening in the light such as dew or fine rain. This rippling, liquid-like nature of light is surprising compatible with the modern quantum physics behavior of photons as both a particle and a wave, but whether Tolkien intended this is unclear.
A word appearing as an element in a couple of untranslated labels for 1960s plant drawings by Tolkien: linquë súrissë “?grass in the wind” and ranalinque “?moon-grass” (TMME/184, 198). This word was also mentioned in a discussion of lassë “leaf” in some Notes on Galadriel’s Song (NGS) from the late 1950s or early 1960s, where Tolkien said “It [lasse] is only applied to certain kinds of leaves, especially those of trees, and would not e.g. be used of leaf of a hyacinth (linque)” (PE17/62). As pointed out by Helge Fauskanger, it is not clear from this note whether linque refers to a “hyacinth” or a “leaf of a hyacinth”. Given the grass-like nature of the two drawings where it appears, I think linque likely means “✱grass or grass-like leaf”.
Neo-Quenya: For purposes of Neo-Quenya I would assume linque applies mainly to grass and grass-like leaves but also to “hyacinth” as an example of a plant with such leaves. If you want to distinguish them, though, Tamas Ferencz proposed the neologism ᴺQ. iasintë “hyacinth” as a loan word from Latin “jacintus”.