late Middle English: from Old French, or from Latin intensus 'stretched tightly, strained', past participle of intendere (see intend)
Intense and intensive are 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 of instruction simply describes the type of course: one that is designed to cover a lot of ground in a short time. On the other hand, in the course was intense, the word intense describes how someone felt about taking the course.