a/c --> account
bcc --> blind carbon copy (copy sent to another person without the knowledge of the main recipient)
cc --> carbon copy (copy to one or more people)
COD --> Cash On Delivery
ETA --> estimated time of arrival
N/A --> not applicable
NB --> nota bene (it is important to note)
PA --> personal assistant
p.a. --> per annum (per year)
p.p. --> per pro (used before signing in a person's absence)
PR --> public relations
R & D --> research and development
re / ref --> with reference to
ROI --> return on investment
RSVP --> repondez s'il vous plait (please reply)