sad/ sæd /

1.adjective
(unhappy) 伤心的

2.adjective
(distressing) 令人悲伤的

3.adjective
(regrettable) 令人遗憾的

4.adjective [inf] 
(pathetic) 可悲的

to be sad about sth
因某事难过
I'm sad that...
…使我伤心
he was sad to see her go
看着她走,他很伤心
it is sad that...
很遗憾…