区别就是两者意思是不一样。

tissue中文意思是n.

(人、动植物细胞的)组织;(尤指用作手帕的)纸巾，手巾纸;(用于包装易碎物品的)薄纸，绵纸;

例句

As we age we lose muscle tissue

肌肉组织会随着我们日趋衰老而萎缩。

napkin中文意思是n.

餐巾;餐巾纸;

例句

He picked the napkin from his lap and placed it alongside his plate

他拿起腿上的餐巾，放在盘子旁边。