A user is a person who uses something, especially a tool, service, or product. When you log into a website, you're a user of that website. When someone downloads an app on their phone, they become a user of that app. Libraries track how many users visit each month. Computer programmers design software with the user in mind, trying to make it easy and intuitive for regular people to operate.

The word became especially common with computers and the internet. Every time you create an account, you pick a username that identifies you as a user of that service. Websites distinguish between regular users and administrators who have special privileges to change settings or manage content.

User can also describe someone who takes advantage of others selfishly. If someone only calls their friends when they need help with homework but ignores them otherwise, those friends might say they're being a user. In this negative sense, a user treats people as tools rather than as friends who deserve care and respect. This meaning carries judgment: nobody wants to be known as a user who only thinks about what others can do for them.