IPA: //diːˈklæsɪfaɪ//
KK: /diˈklæsɪfaɪ/
To remove the official label that restricts access to certain information or documents, making them available to the public.
The government decided to declassify the documents after many years.
Past: declassified
Past Participle: declassified
Declassify → It is formed from "de-" (meaning down or away) and "classis" (from Latin, meaning a class or category). The word means to remove something from a classified status or to lower its classification level.
Think of 'removing' ('de-') something from a 'class' or 'category' ('classis') — that's why declassify means to take something out of a classified status.