Having a great extent; covering a large area; vast. / (figuratively) Considerable in amount. / Serving to extend or lengthen; characterized by extension.

In an extensive manner, widely. / To a great extent.

The degree or property of being extensive.

plural of extensiveness

The act of extending; a stretching out; enlargement in length, breadth, or time; an increase / The state of being extended

Capable of being extended.

The capability of being extended / (computing) A quality of design that takes possible future advances into consideration and attempts to accommodate them

plural of extension

(obsolete) extent; expanse

(obsolete) Outreaching; expansive; extended, superficially or otherwise.