Final answer:
Sex defines biological characteristics distinguishing female and male humans. A romantic and intimate relationship does not require sexual activity as intimacy encompasses more than just sexual interactions; it involves emotional, intellectual, and experiential sharing as well.
Step-by-step explanation:
The term sex refers to the biological characteristics that define humans as female or male. This often includes physical attributes like chromosomes, hormone levels, internal and external reproductive organs, and secondary sexual characteristics. Regarding the question of whether one can be in a romantic and intimate relationship without being sexually active, the answer is yes. Intimacy can be expressed in various ways beyond sexual activities, including emotional, intellectual, and experiential sharing between partners. Such relationships are based on deep emotional connections, trust, and affection, which don't necessarily require sexual activity to be maintained or validated.