Qenya
palan
adverb/adjective. far, distant, wide, to a great extent, over a wide space, to a distance
palantir
noun. far-seer
landa
noun. plain
lanna
noun. plain
landa
adjective. wide, wide, [ᴱQ.] broad
Beware, older languages below! The languages below were invented during Tolkien's earlier period and should be used with caution. Remember to never, ever mix words from different languages!
A noun for “a plain” in the Quenya Verbal System (QVS) of the 1940s derived from ᴹ√LAD “lie flat, be flat” with variants landa and lanna (PE22/126), the latter probably derived from ✱ladna with the voiced stop d becoming a nasal before nasal n. It might simply be the noun form of adjective ᴹQ. landa “wide” from The Etymologies of the 1930s (Ety/LAD).
Neo-Quenya: For purposes of Neo-Quenya, I’d stick to the form landa, which appears in an inflected form landannar “to the plains” early in QVS (PE22/125).