For an additional meaning of "Conjugation", please see marriage.
A conjugation is a derived form of a verb to convey additional meaning, with rules that vary by language.
In 2151, Captain Jonathan Archer instructed Hoshi Sato to attempt to communicate with the Axanar without the universal translator, though Sato stressed she had not even learned the Axanar language's basic conjugations. (ENT: "Fight or Flight")
While on shore leave on Risa in 2152, Sato told Ravis that though she had not heard a language she couldn't learn, it took her months to master the Klingon language's conjugations. On the return trip to Enterprise NX-01, she mentioned learning several new conjugations during her stay. (ENT: "Two Days and Two Nights")