寫信的原則（writing principles）已從原來的3個“c”（conciseness, clearness, courtesy）發展到目前的７個“c”：completeness, clearness, concreteness, conciseness, correctness, courtesy, consideration
實例:
dear sirs,
with reference to your letter of april 9, we are pleased to accept your offer of 100 tons of copper wire as per your offer sheet no.8/070/02b. please go ahead and apply for your export licence. as soon as we are informed of the number of the export licence we will open the l/c by cable.
信的本文漢譯
關於你們四月九日涵，我們高興地接受你們第8／070／02ｂ號報盤單所報100噸紫色銅絲。請著手辦理申請出口許可證。一經接到出口許可證號碼的通知，當即電開信用證。