  An associative central simple algebra is a form of matrices, because a
maximal \'{e}tale subalgebra acts on the algebra faithfully by left and right
multiplication. In an attempt to extract and isolate the full potential of this
point of view, we study nonassociative algebras whose nucleus contains an
\'{e}tale subalgebra bi-acting faithfully on the algebra. These algebras,
termed semiassociative, are shown to be the forms of skew matrices, which we
are led to define and investigate. Semiassociative algebras modulo skew
matrices compose a Brauer monoid, which contains the Brauer group of the field
as a unique maximal subgroup.
