The acceptability of a 15-year-old dating an 18-year-old can vary depending on the laws and cultural norms of the specific region or country. In some places, there are age of consent laws that dictate the age at which an individual is legally able to engage in sexual activities or relationships with others. These laws exist to protect minors from potential exploitation or harm.
If the age of consent in a given location is 18, then a relationship between a 15-year-old and an 18-year-old that involves sexual activities could be illegal, and the older individual could face legal consequences.
Even if the relationship doesn't involve sexual activities and is simply a romantic or emotional connection, there might still be concerns about the maturity and power dynamics between individuals with a significant age gap. It's essential to consider the emotional well-being and safety of both parties involved.
In any case, if you or someone you know is involved in such a situation, it's essential to be aware of local laws, communicate with parents or guardians, and consider seeking advice from a trusted adult or professional counselor to navigate the situation responsibly and safely.