isogloss

noun

iso·​gloss ˈī-sə-ˌgläs 

-ˌglȯs

1

: a boundary line between places or regions that differ in a particular linguistic feature

2

: a line on a map representing an isogloss

isoglossal

ˌī-sə-ˈglä-səl 

-ˈglȯ-

adjective

isoglossic

ˌī-sə-ˈglä-sik 

-ˈglȯ-

adjective

Word History

Etymology

International Scientific Vocabulary is- + Greek glōssa language — more at gloss

First Known Use

1925, in the meaning defined at sense 1