* Comprendre: This is the most common and general word for "understand." It can be used in a variety of situations.
* Saisir: This means "to grasp" or "to catch" and can be used to describe understanding something complex or difficult.
* Appréhender: This translates to "to apprehend" and implies understanding something in a more profound or intellectual way.
* Se rendre compte: This literally means "to make oneself aware" and implies understanding something through personal experience or observation.
Here are some examples:
* Je comprends ce que tu dis. (I understand what you're saying.)
* J'ai du mal à saisir les subtilités de ce texte. (I'm having trouble grasping the nuances of this text.)
* Il a vraiment appréhendé la complexité du problème. (He truly understood the complexity of the problem.)
* Je me suis rendu compte que j'avais tort. (I realized that I was wrong.)
The choice of word will depend on the specific situation and nuance you wish to convey.