A new generation is growing up who have known the internet for their entire lives. More people incorporate social media into more aspects of our lives, including how we learn and negotiate our identities. While formal online classrooms such as MOOCs are a part of the picture, learning also occurs in informal settings such as affinity groups' forums. In the latter spaces, veteran and novice members may interact and engage in ad hoc teaching and learning practices. It is increasingly important to understand the mechanics by which learning functions in these social media forums. One lens we can use is the changing language use practices of novices as they learn. I examine how novices in several Reddit forums change their language production over time to adapt to their communities, focusing on novices' word choice and particularly their use of local jargon. I first demonstrate conditions necessary to separate novices from veterans automatically using machine learning. Through a second statistical analysis of word choice distributions, I find that some novices appear to follow distinct phases of jargon appropriation followed by winnowing. My findings collectively suggest a possible trajectory of language learning in informal online communities. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]