Usual & not unusual

as usual/ usual 像平時一樣，無乜特別

unusual 不平常， 不尋常

not unusual 不是不尋常／少見， 用於有些人少見多怪，覺得某件事少見，而有些人則會應 not unusual， 即不是少見，而時有發生。

It's not unusual, to be mad with anyone It's not unusual, to be sad with anyone but if I ever find that you've changed at anytime it's not unusual to find out that I'm in love with you whoa-oh-oh-oh-oh [ www.azlyrics.com ]
www.azlyrics.com/lyrics/tomjones/itsnotunusual.html - 2k -

嬲人不是不尋常，有甚麼出奇。

It is not unusual for these drawers to be unlabeled. The experienced assistants know exactly where each herb is located. ... It is not unusual to hear of people suffering severe reactions because of overdoses of certain herbs. ...
www.watchtower.org/library/g/2000/11/8/article_01.htm - 18k -

裝中藥的抽屜沒有貼上標籤不是少見。經常見到人因過量服用某些草藥而有過份反應。

可以說，not unusual 意思和 usual 一樣，但語氣是較強調。和中文的 不是不尋常 一樣。

As usual, the sun rises in the east.
It is not unusual that the newly born pig has six legs. 不尋常而己有發生先例