I like splitting it into competency and expertise. In my own personal experience, you can be competent with as many languages as you want, but most people can o

I like splitting it into competency and expertise. In my own personal experience, you can be competent with as many languages as you want, but most people can only hold expertise in a few at a time. Generally, your expertise is going to be the ones you actually use daily, because use is the only way to deepen your understanding. I, for example, and primarily a Java and Python developer during the day, so those are my expertise. Those are the ones I feel confident telling someone to come to me with any questions on, the ones that I know the internals of, the ones I can confidently solve most problems in without having to look much up. As a web developer in my younger days, I considered myself an expert in PHP and Javascript, but I know that I no longer hold that status with them. I could immediately understand if I were to read anything with them, but to start something from scratch I would need some lead-in time, so I'm only going to call myself competent. I use Ruby periodically today, but not on important enough things that I need to understand it deeply, so again I would only call myself competent. I'll sure put all of those on my resume though, along with other competencies and former expertise.