Interleaving.
The person who writes a check is called the payor. Or in the case of my brother, a sucker, when he writes another check for his girlfriend.
partitioning
They are using a pseudonym.
A person that writes for another person's blog under their own name is called a guest blogger. A writer that writes the blogs as the blog owner is called a ghostwriter.
A person who studies or writes history is called a historian.
A "Biographer" is somebody who writes an account of somebody elses life. An "Autobiographer" is a person who writes an account of their OWN life. A "Biographer" is somebody who writes an account of somebody elses life.
A person who writes with their left hand is called left-handed or sinistral.
Pete Wentz is currently in another band called "Black Cards" where he is a bassist and writes lyrics.
The push or pull of one object on another is called by the same name in physics. That term is "force."When one object pushes or pulls another object, this is called force. For example, when a person writes, they are exerting force on the pen.
A person who writes laws is called a legislator or a lawmaker.
Testator.
A person who writes newspaper articles is called a journalist or a reporter.