yet和already都是副词,都表示"已经"一类的意思,但yet用于否定句和疑问句,且用在句子末尾;already用于肯定句,在have或has后.如果要说"最近",就用recently.
另外,yet还当连词用,与although是一组,且有although就只能加yet(不加也行).