Fluctuat nec mergitur (or FLVCTVAT NEC MERGITVR when an inscription written in capitals) is a Latin phrase meaning "She is tossed by the waves, but is not sunk":
- fluctuat: the verb fluctuare in the third-person indicative singular of the present tense in the active voice. Fluctuare means "to be wave-like", "move up and down"; of persons and passions, "to be tossed about", "to waver". In English the verb fluctuare gave to fluctuate.
- nec: contraction of et non, which means "and not", "and does not", "and is not".
- mergitur: the verb mergere in the third-person indicative singular of the present tense in the passive voice. Mergere means "to dip", "plunge into liquid", "immerse", "sink", "overwhelm". In English the verb mergere gave to merge as well as to submerge (literally "merge under", "sub-merge").
The phrase is also the motto of Albert Messiah's classic textbook on quantum mechanics.