for certain 是什么意思啊

know for certain是什么意思? Certain是什么意思? certain materials是什么意思 certain animals是什么意思 certain flavours是什么意思 Certain|y是什么意思? for certain reason还是for a certain reason for certain=certainly吗? English homework:certain newspaper是什么意思? certain what are the causes for certain crimes All i really know for certain