With particular reference to recent developments (including some in communication-technology), this first of two papers explores the nature of "language change"--its kinds, mechanisms and effects--and some attitudes towards it. It then suggests a case for teaching and learning about language change (bearing in mind, particularly, students in the 11-16 age range). The second paper, which will appear in "Changing English" 18:2, suggests approaches of two broad kinds and contexts: (1) as opportunities arise in undertaking other work; and (2) within planned, "set-piece" activities. Extensive notes/references are offered as support to teachers. [For Part Two, see EJ1110494.]