sadly/ 'sædlɪ /

1.adverb
(unhappily) 难过地

2.adverb
(unfortunately) 可惜地

3.adverb [+mistaken] [ neglected] 
(seriously) 完全地

If you think I'm going to leave, you are sadly mistaken.
如果你以为我会离开,你就完全错了。
to be sadly lacking (in sth)
丝毫没有(某物)
he will be sadly missed
大家会很想他的