What Counts As a Portrait?

Google defines a portrait as "a painting, drawing, photograph, or engraving of a person, especially one depicting only the face or head and shoulders" As helpful as this is, it has a lot of holes that need patching up, especially in the context of my project. 

When researching portraits, I came across a lot of fashion plates which got me thinking about what a portrait even is? If I wanted to recreate a gown from a fashion plate, could I?

Under googles' definition, a fashion plates counts as a portrait. This seems a little odd since the goal of fashion plates is not to represent people like a traditional portrait, it's to show the latest trends and styles. An example of the dilemma that this brings up is apparent in Botticelli's The Birth of Venus. Googles' definition technically makes this painting count as a portrait because like in a fashion plate, Venus is a person even if she is not real person. Confusing!

At the end of the day, the goal of knowing what the true definition of a portrait is only to help me understand what I can and can't make during this project. After thinking about these ideas for a while I decided to define what I am allowing myself to consider to be a portrait during the this project, even if I would not agree with this otherwise.

1) A portrait can be of a fictional person
2) A portrait can be a fashion plate 

2) A portrait can be full length

4) A portrait can be a photograph

This definition allows me to venture into the world of fashion plates and fiction making this project just a little bit more exciting. Even so, these rules will always depend on the context.