A convention is seen as a stable habitual behavior, a mechanized way of creation; an innovative original way of creation is called creativity. These terms play different roles in three different situations.
Czech was used as a traditional conventional commucation code in attempting to create a universal Panslavic language, resp. a Czechoslovak language. Formal morphology is a convention which is seen as a time-proven support of codification; creativity is used in the area of texts.
In linguodidactics, semasiology is perceived as conventional, onomasiology as innovative and creative.