inked
Ink
A three letter word for writing quickly is to jot.
The letter 'w'.
aneroid
Fluid
It is not the letter I, but the word "I" that appears too often in many people's writing as the first word in a sentence. Unless you are writing a first-person narrative, good style is to avoid beginning sentences with "I."It is much better to use another word other than I because it is usually a over used word when writing a letter.
A Desk
Written... :)
Paper.
pen
fluid
secret writing= code