An element is another name for an item in a list. (If the same value is in the list twice, that counts as two different elements.) Each element has a unique index (position) in the list.

A sublist is a list as an item of another list.

A data type is what kind of data something is (number, text string, list, etc.).

Each programming language provides some primitive data types (data types that are built-in).

An abstract data type (or ADT) is a custom data type that's meaningful to your program. It's not built into the language; you develop it as you code.

A constructor constructs one example of the data structure.

The selectors select one piece of the data structure.

Data abstraction is the creation and use of abstract data types in a program.

Using the result from item as the input to address from contact is called composition of functions.

Traversing a list means looking at each item of the list. For each is iterative (that is, it's repetitive, like for, which can also traverse a list). But unlike for, for each traverses the list without using index numbers.