the outer boundary of an artifact or a material layer constituting or resembling such a boundary
the extended two-dimensional outer boundary of a three-dimensional object
the outermost level of the land or sea
a superficial aspect as opposed to the real nature of something
chemical agent capable of activity
tending to become more severe or wider in scope
disposed to take action or effectuate change
an active and efficient cause; capable of producing a certain effect
a representative who acts on behalf of other persons or organizations
a substance that exerts some force or effect
