A pen is a writing implement traditionally used to apply ink to a surface, usually paper, for writing or drawing.
In the Almost Human universe, writing with such objects has almost become obsolete. Instead, electronic technology such as computers, tablets, and electronic paper are favored. A pen owned by Kira Larsen, which she and Anton Cross used to write notes to each other with, was given to Detective John Kennex as a thank you for him preventing her from scrubbing away her memories of Anton. Kennex used the pen and some paper to write a note to Detective Valerie Stahl.
Pens have been seen on desks in the Detective and Investigation unit of the Police Precinct, but it has not been confirmed if these are tablet pens or traditional pens.