Here are some options:
Formal:
* 彼女 (kanojo): This is the most common and neutral way to refer to a girlfriend. It literally means "she" but is used for both girlfriends and wives.
* 恋人 (koibito): This means "lover" and is a more formal way to refer to a significant other.
Informal:
* カノジョ (kanojo): This is the casual pronunciation of 彼女.
* 彼女さん (kanojo-san): This is a slightly more polite way to refer to your girlfriend, adding the honorific "-san."
* (Name)ちゃん (Name-chan): You can use your girlfriend's name followed by the suffix "-chan," which is a term of endearment used for girls and young women.
Other Options:
* 彼氏 (kareshi): This means "boyfriend" but can be used in some situations to refer to your girlfriend, especially if you want to emphasize your relationship. For example, "私の彼氏 (watashi no kareshi)" could mean "my boyfriend" or "my significant other."
* 愛人 (aijin): This means "lover" and is a more poetic term, but it can also have a negative connotation, suggesting an extramarital affair.
It's important to note that the best way to refer to your girlfriend depends on your relationship and the context. It's always a good idea to ask your girlfriend how she prefers to be addressed.