"Intense" and "intensive" are two different words:
If you are putting forth an intense effort, your work is “intense”: “My intense study of Plato convinced me that I would make a good leader.” But when the intensity stems not so much from your effort as it does from outside forces, the usual word is “intensive”: “the village endured intensive bombing.”
Is there any way to understand why the word ending in "se" has one meaning, and the word ending in "sive" has another meaning?
The reason these two words have different endings is because they grew from two different root words in Old French, which helped form Old (and Modern) English.
Intense came from the French word intensus, meaning "stretched, strained, tight".
Intensive came from the English word intend, which in turn came from the French words entendre and intendre (essentially the same word), which means "to direct one's attention to".
Interestingly, both of these French words have the same Latin root word intendere, which is literally "to stretch tight", but entendre took a separate path in terms of connotation and meaning and developed into the word we have now.
Intensive is something that is intense. Simply put intensive is used to talk about something that is sustained, where as intense is more linked to feelings. Intensive is usually used to talk about something outside of you, whereas intense commonly refers to something you felt, or did.
Sourced From here on Dictionary.com
BAD: The government has embarked on an intense industrialization programme.
GOOD: The government has embarked on an intensive industrialization programme.
intense = strong or very great; extreme: 'intense heat', 'intense pleasure', 'intense pain', 'intense competition'
intensive = concentrated: 'an intensive English course', 'a period of intensive training'
