Amy Farrah Fowler

Dr. Amy Farrah Fowler is a neurobiologist . Raj and Howard met Amy through an online dating site after secretly setting up an account using Sheldon's name and information. The site matches her to Sheldon, and the two share many similar traits. Once she and Sheldon meet, she becomes, as Sheldon puts it, a girl who is his friend, but not his "girlfriend". They briefly ended their friendship when they got into an argument over whose field of study was superior. The two initially communicate only by text message and occasionally via webcam, though she gradually began hanging out with the gang in person through the fourth season. 
Amy Farrah Fowler is portrayed by Mayim Bialik.