What is a mature hairline? I want to know more. I am a 21 year old male experiencing mature hairline.

Several years ago I wrote a blog article on this topic. You may wish to review the link below to help you better understand this important topic.

When we talk about mature hairlines, we are referring to the idea that the hairline we design today should look appropriate as you age. We try to avoid hairlines that are too straight or too low.  Most male hairlines have a gentle curve to it and some asymmetry.  In order to know what this really means, you need to come in for an in-person consultation.  At that time, we can show you what would look good aesthetically and what kind of hairline would "fit" your face.  

Men change from a rounded hairline to a V-shaped hairline between the ages of 17-29, see the post writen about this process with photos below