mindmap root((虚假无礼卧倒口语确定)) sure usually stresses a subjective or intuitive feeling of assurance: felt ~ that he had forgotten something. certain may apply to a basing of a conclusion or conviction on definite grounds or indubitable evidence: scientists are now ~ what caused the explosion. positive intensifies sureness or certainty and may imply opinionated conviction or the forceful expression of it: she is ~ that he is the killer. cocksure implies presumptuous or careless positiveness: you're always so ~ about everything.