areal adjective. 
['ɛ:rɪǝl] L17.[from AREA + -AL1.]1.  Of, pertaining to, or of the nature of an area. 
L17.2.  Linguistics. Of or pertaining to geographical factors as determinants of the relationship or development of languages or dialects. 
M20.areal linguistics a school of linguistics emphasizing geographical factors in language development and distribution.
 ■   areally adverb with regard to area 
M20.  [TahlilGaran] English Dictionary ▲