The terminology of “themes” is taken from the idea of theme-based roadmaps, but “objectives” could be used as well to make the link to OKRs clearer. I think using the word “themes” as opposed to “objectives” has the advantage that a theme might span multiple goal-setting periods and the objectives for the theme might change slightly. For example, the theme may be “Improve onboarding” and have the objectives “Improve sign-up conversion” in the first quarter and “Improve new user activation” in the second quarter.