ill与sick这两个形容词均有“生病的”之意。
ill : 在英国较常用，指“生病”时，通常作表语，不可作定语。在美国，ill用作表语时可与sick换用。
- I felt ill so I went home.
我感到不舒服，于是就回家了。 - He's been ill with meningitis.
他得了脑膜炎。 - Sophia fell ill/was taken ill (= became ill) while on holiday.
索菲娅在休假时生病了。 - He is critically (= very badly) ill in hospital.
他在住院，病得很重。
sick多用于美国，作“生病”解时，既可作表语，也可作定语。在英国，sick作表语，不指生病，而指“恶心、呕吐”。
- a sick child
生病的孩子 - a sick cow
病牛 - My father has been off sick (= not working because of illness) for a long time.
因为生病，我父亲已经很久没有去上班了。 - Anyone who could hurt a child like that must be sick (= mentally ill).
那样伤害一个孩子的人，脑子一定有毛病。
