Hi there, Jaw definition can be affected by a few things: 1. The bony position of your lower jaw (mandible) to your upper jaw (maxilla). For example, your mandible could be retruded or protruded or even at be in excess or deficient from a vertical standpoint. It's hard to tell without an x-ray to appreciate your bony relationship. However, from you profile view, it looks like you might be a little deficient vertically, notably in your chin area. This could be address either with a chin implant or some type of jaw surgery if it was deemed appropriate. 2. Skin laxity. There is some "jowling" that I can appreciate from your profile photo. This can be due to skin laxity with time or again be related to the position of your jaw or chin. Jowling and major skin laxity is addressed is with either a face/neck lift, although, I considering how young you are this isn't something I would recommend right away without a proper clinical workup. 3. Volume. This is where dermal fillers might help add definition to your lower jaw if you are looking for a less invasive option. Dermal fillers come with there own set up pros and cons, but this is something you could discuss with an experienced injector &/or surgeon. My recommendation to you would to be evaluated by a facial surgeon to understand which option could best benefit you in achieving your goals. Hope this helps!