* καταλαβαίνω (katalamainō): This is probably the closest general equivalent. It implies grasping the meaning of something, comprehending, or perceiving. It's a very common and versatile word.
* συλλαμβάνω (sylllambanō): This word implies grasping or seizing an idea; understanding something intellectually. It suggests a more active process of comprehension.
* επινόω (epinoō): This means to understand, comprehend, or conceive of something, often implying insightful understanding or devising a plan based on that understanding.
* γινώσκω (ginōskō): While often translated as "know," this word can also convey understanding, especially in the sense of having knowledge that allows for understanding. The context is crucial here.
* νοώ (noō): This word emphasizes mental comprehension and awareness. It often implies a deeper, more intuitive understanding.
The best word to use will depend heavily on the context. If you can provide a sentence where you'd use "understand," I can give you a more precise Greek equivalent.