The phrase "a user and a" is grammatically correct and can be used in written English.
It can be used when referring to multiple entities or roles, typically in a context where you are discussing different types of users or participants.
Example: "In our system, we have a user and a moderator who both play crucial roles in maintaining the community."
Alternatives: "a user and a participant" or "a user and an administrator".
Heads from the companies Spotify, SoundCloud (I'm a user and a big fan of theirs, by the way), Songkick and MusicGlue made presentations, followed by a Q&A.
Their uneventful friendship is interrupted by the arrival of Rose (Misty Wilkins), a slender and pretty girl but a user and a thief.
These could allow a hacker to intercept information moving between a user and a service like Gmail that appeared to be secure.
Intelligence agencies can also tap data cables, allowing them to capture unscrambled information being sent between a user and a server, regardless of whether it is later encrypted.Mr Snowden's leaks seem to have boosted the market for better ways of dealing with this behaviour, too.
The most fundamental interaction between a user and a product is physical touch.
Private information retrieval (PIR) is normally modeled as a game between two players: a user and a database.
He likes the concept so much that he signed on to the SkyGo trial as both a user and an advertiser.
Meanwhile, the closer a user and an item are in feature space, the higher the predicted rating will be.
The 802.1x standard is used for securing the transfer of messages between a user and an access point.
An entity is any information that is considered relevant to the interaction between a user and an application including the user and applications themselves".
Web 2.0 tools (including among others social networks, wikis, mashups and tags) aim at allowing a better interaction between a user and an Internet site, or between communities of users by means of a Web site.
