Bare-root Adverbs
Other adverbs occur as bare roots; the distinction between bare-root and -aŭ adverbs is lexical. However, some of the bare-root words may be argued to be grammatical particles and not true adverbs, in which case true adverbs may be derived from them by adding the ending -e. They are,
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Esperanto English notes for away cf. the derived adverb fore jam already, yet ĵus just now nun now noun and adverb nur only plej most cf. the derived adverb pleje pli more pronoun and adverb; cf. the derived adverb plie plu beyond, further cf. the derived adverb plue tre very tro overly, too much cf. the derived adverb troe tuj at once, immediately
Occasionally in poetry forms such as nune and tree are seen, but this is considered grammatically redundant (Kalocsay & Waringhien 1985:409).
Read more about this topic: Special Esperanto Adverbs