Here are some options:
Informal:
* 彼氏 (kareshi): This is the most common and direct way to say "boyfriend." It's informal and used with close friends or within a couple.
* 彼 (kare): This is a more casual and shortened version of "kareshi." It's usually used between close friends or in playful situations.
Formal:
* 恋人 (koibito): This word means "lover" and can be used for both boyfriend and girlfriend, regardless of gender. It's more formal and can be used in situations where "kareshi" would be inappropriate.
* パートナー (pātonā): This word means "partner" and is often used in a more neutral and professional context, such as in a business setting.
Other:
* You can also use the person's name directly, followed by a term like "彼 (kare)" or "彼女 (kanojo)," depending on the gender.
The best way to choose the right term is to consider the context and the relationship between the speaker and the listener.