Horizontal form
Encyclopedia
A differentiable r-form
on a fiber bundle
E is said to be a horizontal form if
whenever at least one of the vectors 
is vertical
.
Differential form
In the mathematical fields of differential geometry and tensor calculus, differential forms are an approach to multivariable calculus that is independent of coordinates. Differential forms provide a better definition for integrands in calculus...
on a fiber bundleFiber bundle
In mathematics, and particularly topology, a fiber bundle is intuitively a space which locally "looks" like a certain product space, but globally may have a different topological structure...
E is said to be a horizontal form if
whenever at least one of the vectors is verticalVertical bundle
The vertical bundle of a smooth fiber bundle is the subbundle of the tangent bundle that consists of all vectors which are tangent to the fibers...
.