a person who makes use of a thing; someone who uses or employs something
"The new coffee machine had a steep learning curve for every user until they finally mastered the settings."
a person who takes drugs
"The social worker spent hours trying to convince the user that seeking help was the best way forward."
One who uses or makes use of something, a consumer/client or an express or implied licensee (free user) or a trespasser.
"The new app requires users to log in before they can access any premium features."
In plain English: A user is someone who operates or makes use of something, like a computer program or an app.
"Every user can customize their profile settings in just a few clicks."
Usage: Use "user" to refer generally to anyone operating a system or product; avoid it when specifically addressing customers in sales contexts where "client" or "customer" is more precise. The term remains neutral and applies equally to casual consumers, licensed professionals, and unauthorized individuals depending on the situation described.
The word user comes from Middle English by adding the suffix -er to the verb use. It entered English in a straightforward way without any major shifts in meaning over time.