Bacterial Vaginosis (BV): This is the most common cause of abnormal vaginal discharge, characterized by a fishy odor and thin, greenish or grayish discharge. The imbalance of normal vaginal flora leads to an overgrowth of anaerobic bacteria, resulting in the symptoms.

Trichomoniasis: A sexually transmitted infection caused by the parasite Trichomonas vaginalis, leading to a greenish, frothy, and foul-smelling discharge. It's a common cause of vaginal infections and can be associated with other sexually transmitted diseases.
Gonococcal Infection: Caused by Neisseria gonorrhoeae, this sexually transmitted infection can lead to a greenish or yellowish discharge, often accompanied by pelvic pain and other symptoms.
Chlamydial Infection: Another sexually transmitted infection, caused by Chlamydia trachomatis, which can result in a greenish discharge, though it's more commonly associated with other symptoms like dysuria and pelvic pain.

Pelvic Inflammatory Disease (PID): While not always presenting with green discharge, PID is a serious condition that can result from untreated sexually transmitted infections. It involves infection of the upper genital tract and can lead to severe complications like infertility and chronic pelvic pain if not promptly treated.
Cervical Cancer: Though rare, advanced cervical cancer can cause abnormal vaginal discharge, including greenish discharge, due to tumor necrosis. Early detection through screening is crucial.

Foreign Body: The presence of a foreign body in the vagina, especially in children, can lead to a greenish discharge due to the accumulation of bacteria and debris around the object.
Vaginal Tumors: Benign or malignant tumors of the vagina can cause abnormal discharge, including greenish discharge, though this is exceedingly rare.
Diverticulitis of the Vagina: A rare condition where a diverticulum (pouch) in the vaginal wall becomes inflamed, potentially leading to abnormal discharge.