小心

be careful; watch; beware; look out; take care; watch out; careful; close; safe; chary; cautious; wary; painstaking; religious about; circumspect; carefully; cautiously; narrowly; studiously; easy; steady; caution; care; respect; heads up

当心

be careful; mind; watch; beware; take care; watch out; look out; heed; take heed; tread carefully; pay attention; keep an eye out; in the middle; in the centre; in the midmost; careful; cautious; watchful; alert; wary