It is hard to change one's essential nature (idiom). You can't change who you are. / Can the leopard change his spots? (Jeremiah 13:23)
江山易改，本性难移
jiāng shān yì gǎi , běn xìng nán yí
it is easier to change mountains and rivers than to alter one's character (idiom) / you can't change who you are / Can the leopard change his spots?
飞蚊症
fēi wén zhèng
eye floaters (moving spots in the eye's vitreous humor)
湘妃竹
xiāng fēi zhú
same as 斑竹[ban1 zhu2], mottled bamboo, since according to legend the spots on mottled bamboo are marks left by the tears shed by two of King Shun's 舜[Shun4] concubines (Ehuang 娥皇[E2 huang2] and Nüying 女英[Nu:3 ying1], known as the Concubines of the Xiang 湘妃[Xiang1 Fei1]) upon learning of his death
yǎn