卫生间 (wèi shēng jiān) is the most neutral, polite word for 'bathroom' or 'toilet' in everyday Chinese — it literally means 'sanitary room'. 洗手间 (xǐ shǒu jiān, 'washroom') is slightly more euphemistic and common in public places, while 厕所 (cè suǒ) is blunter and can sound crude in some contexts. 浴室 (yù shì) specifically refers to a room for bathing, not a toilet.