# Glossary

Ancestor
An element in a tree is an ancestor of another if it is its parent or an ancestor of its parent. For example, in the tree view, an element representing `IF(A1 = 0, B2, C3)` is an ancestor of an element representing `A1`.
Atomic expression
An expression, such as `5`, `"abc"`, and `A1`, that cannot be decomposed into smaller expressions and are displayed at the bottom of the tree view.
Canvas
A floating window, with no limitations on its width, in which Formula Forge can displayed when Excel's task pane is too narrow.
Child
An element in a tree that has a parent. In the tree view, a child appears below its parent. For example, elements representing the expressions `A1` and `B1` appear as children of an element representing the expression `A1 + B1`.
Compound expression
An expression, such as `A1 + 5` and `IF(A1 = 0, B2, C3)`, that can be decomposed into smaller expressions.
Descendant
One element in a tree is a descendant of another if that other element is one of its ancestors. For example, in the Tree View, an element representing the expression `A1` is a descendant of an element representing the expression `IF(A1 = 0, B2, C3)`.
Element
An instance of an expression. For example, the expression `A1 + B1` may occur more than once in a formula. Each occurrence is an element of the formula.
Ellipsis
Two or three dots used to abbreviate an expression or a string, as in `IF(..., A1, B1)` and `"This .."`.
Expression
A string that can represent a formula in Excel. An expression can be an atomic expression, which cannot be decomposed into smaller expressions, or a compound expression, which can.
Formula
An expression, such as `A1 + 2`, obtained from a cell in Excel whose contents begin with an equal sign (i.e., from a cell with `=A1 + 2` as its contents).
Formula views
Formula Forge's text view, math view, and tree view.
Hover
An event that occurs when a user moves or hovers the cursor over some element of a graphical user interface. See tooltip.
Math view
A representation of a formula, similar to those found in typeset mathematics and engineering textbooks, that employs standard mathematical symbols and uses standard typographic conventions (e.g, for numerators and denominators in fractions).
Pane
The rectangular area in which Formula Forge is displayed, either to the right of the spreadsheet in Excel's window or in a floating canvas. Sometimes known as a "task pane".
Parent
An element in a tree that has a child. In the tree view, the parent appears above each of its children.
Reference
In Excel, an identifier for the location of a cell (e.g., `A1`, `\$B\$35`) or a range of cells (e.g, `C1:E10`, `\$A:\$B`, `\$100`).
Selection
The element currently selected by the user. A selection is highlighted in blue in the math view, text view, and tree view.
Sibling
An element in a tree with the same parent as another element. Any two children of a single element in a tree are siblings of each other. For example, in the tree view, an element representing`A1 + B1` has two children, representing `A1` and `B1`, which are siblings of one another.
Tooltip
A box of information that appears when the cursor hovers over an element (such as a button) in a graphical user interface.

Tooltips provide information about elements in the tree view.
Top element
The unique element in a tree that is an ancestor of every other element in the tree. In the tree view, the top element represents an entire formula.
Text view
A representation of a formula as a string of characters that is recognized, when preceded by an equals sign, as input to Excel.
Tree
A nonempty set of elements, some of which are children of other elements. Each tree has the following properties:
• Each element is the child of at most one other element, called its parent.
• The children of each element are ordered from left to right.
• There is exactly one element in a tree, called its top element, that has no parent. This top element is an ancestor of every other element in the tree.
Tree view
A hierarchical representation of a formula or an expression as a tree. Similar in appearance to an organization chart.