Do I call it a Plectrum or Pick, this is a question passed from generation to generation of guitarist and to their siblings, I have found so far that what you call the trusty guitar pick could come down to where you live, the age of your guitar teacher, your parents or the books you are reading to learn about guitar.
A simple answer for plectrum or pick is a guitar pick is that both are correct and guitar pick is just a specific name for a sub group of the trusty plectrum, the guitar picks are plectrums for guitars, there are plectrums for other stringed instruments.
This brief look into the plectrum/guitar pick follows on from my writings on the guitar so far, types, parts, brands, history and more are covered in what I have already written about in the guitar music section.
Guitar picks come in many different sizes, shapes and thickness, there is many different types of materials used also, these may include, plastic, nylon, rubber, tortoise shell, wood, metal, glass, stone and aluminum to name a few.
The shape of the guitar pick can vary from company to company but most retain the standard isosceles triangle shape with two rounded corners at the top and varying roundness at the string contact end depending on personal taste and the brand of pick.