Only when written 努努 / 努々
Used in expressions of prohibition, often with ～な or ～まじ; literary and somewhat archaic.
You must never forget.
Used with negative verb forms; emphasizes complete absence or prohibition. Literary and rare.
You must not doubt even a little bit.
Only when written 努努 / 努々
Rare adverbial use meaning 'diligently'; mostly found in older texts.
The teacher said, 'Work diligently.'
Kanji form used for the adverbial senses; rare and mostly literary.
Kana spelling is practical for all senses, especially for learners.
Variant of 努努 with iteration mark; rare.
Kanji form used for the noun sense 'dreams'; rare.
Variant of 夢夢 with iteration mark; rare.
The historical derivation is uncertain. The kanji 努 (effort) and 夢 (dream) are used as ateji for the reading ゆめゆめ, which may be a reduplicated form of ゆめ (dream) or an emphatic expression.