The three other characters are all pronounced ce4:
- Adding three drops of water at the side produces 测 cè 'measure'.
- 人 rén 'man' + 则 rule = 'side': 侧 cè
- Putting a roof on produces 厕 cè 'toilet', although it is not very clear how this relates to the other three from a meaning point of view!
Common words including these characters:
原则 yuánzé 'principle'
猜测 cāicè 'to conjecture'
侧面 cèmiàn 'side'
厕所 cèsuǒ 'toilet'