(1) What's the difference between "astronaut" and "spacewalker"?
(2) When we say that "rice has been a staple of Hopi diet for centuries", what's the meaning of "staple" here? Doesn't it mean the important part?
Please put questions that are not related to each other in separate posts.
You should try to write in correct English, especially if you are a teacher.
(1) An astronaut is somebody trained to travel in outer space. Some astronauts are required to walk in space, some are not. So not all astronauts are spacewalkers.
(2) Yes, here "staple" means the main part or a very important part of the diet.
not a teacher