So far we specified the elements of sets by verbally. The roster form introduced here offers a concise way of writing down sets by listing all elements of the set. Furthermore we use ellipsis to describe the elements in a set, when we believe that the reader understands how a pattern in a list of elements continues.
The contents of a set can be described by listing the elements of the set, separated by commas, inside a set of curly brackets. This way of describing a set is called roster form.
\(\{\mathtt{w}, \mathtt{x}, \mathtt{y}, \mathtt{z}\}\) is the set containing the letters \(\mathtt{w}, \mathtt{x}, \mathtt{y}\text{,}\) and \(\mathtt{z}\text{.}\)
Recall that an ellipsis (\(\ldots\)) indicates that the pattern is continued. We can use an ellipsis when writing a set in roster form instead of listing every element.