Adversaria (ahd wehr SAH ree uh), literally "that which has been turned to", is a plural noun referring to notes or brief written comments: "Her adversaria were fascinating in their perceptions." It also refers to annotations or commentaries written on a facing page of a book.

As a singular noun, an adversaria (ad vuhr SAY ree uh) is a journal or commonplace book, a book used for recording one's observations as well as for collecting poems, brief essays, and any other material one finds worth keeping.