Okay kiddo, so "hospitalism" is a big word that describes something that can happen when babies or young children have to stay in the hospital for a long time.
See, hospitals are great places for getting better when we are sick or hurt, but they can also be kind of lonely and scary sometimes. And when kids have to stay there for a long time, they might not get the same attention and love that they would at home.
Now, here's where it gets a little complicated. When kids are not getting enough attention and affection from others, it can affect their growth and development. They might become less curious, less active, and less willing to explore their surroundings. This is what we call "hospitalism."
But don't worry, buddy. Hospitals know all about hospitalism and they work really hard to make sure that kids get lots of love and attention while they are there. There are lots of nurses and doctors and other grown-ups who take care of them and try to make them feel better. And most importantly, parents and loved ones can come and visit them as much as possible to give them all the extra hugs and cuddles they need.