In a sufficient manner; enough.
"The new bridge was sufficiently reinforced to withstand even the strongest earthquakes."
In plain English: Sufficiently means enough to meet what is needed for something to work properly.
"The team waited until they had sufficiently gathered all the necessary materials before starting the project."
The word sufficiently is formed by adding the suffix "-ly" to sufficient. It entered English directly from Latin through French without a significant shift in its core meaning of being enough.