隐(yǐn)私(sī) means ‘privacy’ while 私(sī)事(shì) means ‘personal affairs’.
In Chinese, it is frequent to match 隐(yǐn)私(sī) with 个(gè)人(rén) ‘individual’, for example:
请(qǐng)保(bǎo)护(hù)你(nǐ)的(de)个(gè)人(rén)隐(yǐn)私(sī)
Please protect your personal privacy
While 私(sī)事(shì) versus 公(gōng)事(shì) and is usually used as:
这(zhè)是(shì)我(wǒ)的(de)私(sī)事(shì)，与(yǔ)你(nǐ)无(wú)关(guān)
This is my personal affairs, which is none of your business.
