breadth: how wide something is, the measure across it from side to side.
This is the plain word for width, the side-to-side measure of a thing. It almost always sits beside its partners for length and height when the Bible records the exact size of something built: the ark, the tabernacle and its curtains, the altar, the temple and its rooms, a bedstead, a flying scroll. Wherever a precise dimension is given, this is the across measurement.
The same word stretches naturally from a built object to open ground. The land God tells Abram to walk through, the surface of frozen water, a flood that fills the whole width of a country: in each case it names how far a thing reaches sideways. The idea does not change, only the size of what is being measured.
From that physical picture grows a single figurative use. When Solomon is given breadth of heart, the word keeps its spatial sense but applies it to the mind: a wide, roomy understanding with space enough to hold knowledge as vast as the sand on the seashore. It is the same width, pictured on the inside of a person.