breadth

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The measure or dimension from side to side; width.
• noun A piece usually produced in a standard width.
• noun Wide range or scope.
• noun Tolerance; broadmindedness.
• noun An effect of unified, encompassing vision in an artistic composition.

from The Century Dictionary.

• noun The measure of the second principal diameter of a surface or solid, the first being length, and the third (in the case of a solid) thickness.
• noun Hence Figuratively, largeness; freedom from narrowness or restraint; liberality: as, breadth of culture, breadth of view, etc.
• noun That quality in a work of art, whether pictorial or plastic, which is obtained by the simple, clear rendering of essential forms, and the strict subordination of details to general effect.
• noun In logic, extension; an aggregate of subjects of which a logical term can be predicated.
• noun Something that has breadth; specifically, a piece of a fabric of the regular width; a width.

from the GNU version of the Collaborative International Dictionary of English.

• noun Distance from side to side of any surface or thing; measure across, or at right angles to the length; width.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The extent or measure of how broad or wide something is.
• noun A piece of fabric of standard width.
• noun Scope or range, especially of knowledge or skill.
• noun mathematics (graph theory) the length of the longest path between two vertices on a graph

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the extent of something from side to side
• noun the capacity to understand a broad range of topics