in full control of your faculties; "the witness remained collected throughout the cross-examination"; "perfectly poised and sure of himself"; "more self-contained and more dependable than many of the early frontiersmen"; "strong and self-possessedin the face of trouble"
An author's collected works or letters are all their works or letters published in one book or in a set of books. the collected works of Rudyard Kipling = complete
brought together in one place; "the collected works of Milton"; "the gathered folds of the skirt
If you say that someone is collected, you mean that they are very calm and self-controlled, especially when they are in a difficult or serious situation. Police say she was cool and collected during her interrogation. see also collect