mildly          
adverb uk/ˈmaɪld.li/ us/ˈmaɪld.li/
 略微地
slightly
  I was mildly surprised to see him here. 在这里看到他令我略感惊讶。 
  温和地
in a gentle way
  "I think you've made a mistake," he said mildly. “我认为你犯个了错误。”他温和地说。 
 Idiom   
to put it mildlyidiom  保守地说;说得好听(或委婉)一点
used for saying that something is much more extreme than your words suggest
  It has been a remarkable day, to put it mildly. 说得委婉一点,这是不寻常的一天。