The word "de" usually acts as a prefix that means "remove" or "reverse." Therefore, the antonyms for this word would be terms with prefixes that signify "add" or "continue." Some examples of antonyms include "renew," "recommence," "enact," "perpetuate," and "resurrect." These words denote actions that move forward, rather than ones that reverse or undo past actions. In contrast to "deactivate," an antonym could be "activate." In the context of language, learning antonyms can help you to expand your vocabulary and communicate more effectively.