An informant is someone who gives another person a piece of information. 信息提供者
noun [专属名词]信息提供者,告密者;资料提供人,合作者
On the basis of data furnished by her informants, Mead concluded that adolescents in Samoa had complete sexual freedom. 米德根据信息提供者所给的资料,得到的结论是萨摩亚的青少年有完全的性自由。