Speaking of one-letter words, Annie Dillard collected her favorite maritime navigation codes, such as:

A  -  I am undergoing a speed trial.

D  -  Keep clear of me; I am maneuvering with difficulty.

F   -  I am disabled. Communicate with me.

G  -  I require a pilot.

F  -  Your lights are out, or burning badly.

U  -  You are standing into danger.

X  -  Stop carrying out your intentions.

K  -  You should stop your vessel instantly.

L   -  You should stop.  I have something important to communicate.

Our favorite:

R   -  You may feel your way past me.