【Broad】 , 【wide】 , 【deep】 are comparable chiefly when they refer to horizontal extent.

【Broad】 and 【wide】 apply to surfaces or areas as measured from side to side and 【deep】 (see also 【DEEP】 ) to those as measured from front to back.

【Broad】 and 【wide】 always and 【deep】 in some instances may be used of surfaces that spread away from one; thus, a river may be 【wide】 or 【broad】 (but not 【deep】 , which would here refer only to vertical distance) at a given point, but a flower border may be four feet 【wide】 ,  【broad】 , or, if the far side is not ordinarily accessible,  【deep】 .

When a plot of ground or similar area is measured,  【broad】 or, especially, 【wide】 is used of the distance from one side to the other and 【deep】 of that from front line to back line.

【Broad】 and 【wide】 are frequently interchangeable when used descriptively to mean having relatively great extent across or from side to side.

But 【broad】 commonly applies only to surfaces or areas as such.

【Wide】 applies also to apertures or to something that opens or spreads. 【Wide】 , therefore, is the preferred term when the emphasis is upon the distance between limits rather than on the extent of the intervening surface.

【Deep】 in similar descriptive use, when it carries an implication only of horizontal extent, is applicable only to something that has great extent backward (as from an opening or from the front).