Conjugate is what you do to a word to make it agree with other words in a sentence. If you’ve studied a foreign language, you know that sometimes you can conjugate a verb just by changing its endings.
To conjugate the verb to be, you’d say “I am,” “you are,” “she is,” and so on. You’re changing the form of the verb to make it agree with the subject. You might conjugate other words to make them agree in number, gender, or tense. In chemistry, conjugate means "to join together." It can also be an adjective, meaning "joined," or "joined in pairs," like the conjugate leaf of an Oak tree.