adjective (intenser, intensest)
late Middle English: from Old French, or from Latin intensus 'stretched tightly, strained', past participle of intendere (see intend)
Intense and intensive are clearly similar in meaning, but they differ in emphasis. Intense tends to relate to subjective responses—emotions and how we feel—while intensive tends to relate to objective descriptions. Thus, an intensive course simply describes the type of course: one that is designed to cover a lot of ground in a short time, e.g. by being full-time rather than part-time. On the other hand, in the course was intense, intense describes how someone felt about the course.