Youngsters these days are so engrossed in their studies that they do not have much free time to enjoy themselves.

engrossed 是动词 engross 的过去分词形式，engross 由前缀 en-（表示"使进入某种状态"）和 gross（"全部的"）组成，字面意思是"使完全投入"。engrossed 表示"全神贯注的、完全沉浸于某事的状态"。