The science of diplomas, or the art of deciphering ancient writings and determining their age, authenticity, etc.; paleography.
"The museum director hired an expert in diplomatic to authenticate the newly discovered medieval manuscripts before they went on display."
In plain English: A diplomat is someone who represents their country and handles official business with other nations through polite conversation instead of fighting.
"The ambassador's main diplomatic was to keep peace between the two rival nations."
using or marked by tact in dealing with sensitive matters or people
"the hostess averted a confrontation with a diplomatic chenage of subject"
Concerning the relationships between the governments of countries.
"The ambassador held a series of diplomatic meetings to resolve the trade dispute between the two nations."
In plain English: Diplomatic means handling tricky situations carefully and politely so you don't make anyone angry.
"She gave a very diplomatic answer that avoided offending anyone at the meeting."
Usage: Use diplomatic to describe actions that maintain peaceful relations between nations rather than personal tactfulness in social situations. This word specifically refers to official government interactions instead of general courtesy or skillful handling of individuals.
The word comes from the Old French diplomatique and ultimately from New Latin diplomāticus. It originally described matters related to a diploma or official document before entering English with that same sense.