Critical terms must be clearly and consistently used. 

For example, UK law recognises protected titles; ‘general practitioner’, ‘registered nurse’, or ‘paramedic’ have specific meanings, and to use one carries legal weight. Interestingly ‘surgeon’ appears on the GMC’s list of legally protected titles, but ‘anaesthetist’ does not.

While meaning can appear clear from context, ambiguity creates risk. It need not be highly technical terminology to cause problems. Misunderstanding of ‘OK’ contributed to the 1977 Tenerife air disaster, where a tower controller probably intended ‘I acknowledge your request to take off’, but the flight commander understood ‘you are giving me clearance for take-off’. The Boeing 747 accelerated down the runway, and shortly thereafter collided with another aircraft.