Every developer no matter what level of expertise has their views and opinions when it comes to programming language choices. It's much like a toolbox, you use them based on the specific need you have to solve a problem or fix something. One of the Chief Scientist at Salesforce wrote a blog about this in which they stated that software programming is developing, due to deep-learning algorithms, which review large amounts of information and can better handle messy or "unstructured" data, including human language. One of the reasons an interviewer will ask this question is to see what range of tools you have used, and which you prefer using. they also want to see if you are familiar with the latest developments in programming. It always helps to start by stating that you have used several languages and have a high confidence level with all of them, but if you had to pick, give them a range and narrow them to one of your favorites. Don't be surprised if an interviewer asks why you like that language, and what benefit it gives you. If the interview is going well, it wouldn't be a bad idea to talk about some of the strengths and weaknesses of a few that you have used. As a reference, the top languages likely be Python, Java, JavaScript, C, C#, Ruby, PHP, Swift and SQL.