Middle Primitive Elvish
dimbā
adjective. sad, gloomy
dem
root. sad, gloomy
There are more words but they are from Tolkien's earlier conceptional periods. Tolkien likely changed these words as he evolved the aesthetics and completeness of the languages. You may even find languages that Tolkien later rejected. Do not mix words from different time periods unless you are familiar with the phonetic developments.
Below: Tolkien's Late Period (1950–1973). These are from Tolkien's late conceptual period — his most settled forms of the languages. Prefer these over the earlier ones above when composing new text.
An Ilkorin-only root in The Etymologies of the 1930s glossed “sad, gloomy” (Ety/DEM). It was first given as √DIM, which Tolkien rejected and replaced by √DEM (EtyAC/DEM), but given the Ilkorin name Dimbar in both The Etymologies and contemporaneous Silmarillion drafts (LR/261), Tolkien likely reversed himself and restored √DIM. In later iterations of The Silmarillion, it is likely that S. Dimbar became a Sindarin name.