Gnomish
ladwen
noun. levelness, flatness; plain, heath; plane; surface
ladwen-na-dhaideloth
place name. Heath of the Sky-roof
bladwen
noun. plain
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.
A noun in the Gnomish Lexicon of the 1910s glossed “a plain” (GL/23), probably derived from the root ᴱ√PALA “flatness” as suggested by Christopher Tolkien (LT1A/Palúrien; QL/071).