The parameters with respect to acetabular orientation, including anteversion and inclination, are important for preoperative planning, intraoperative guide and postoperative evaluation for total hip arthroplasty (THA). Malposition of the acetabular component in THA is a major risk factor to reduce the service life of the prosthesis. At present, several definitions are available for the acetabular anteversion and inclination, whereas there are different expressions for one definition. It will make the clinicians confused if these definitions are not elucidated clearly.