to the greatest degree or extent; completely or entirely; (`full' in this sense is used as a combining form)
"fully grown"
"he didn't fully understand"
"knew full well"
"full-grown"
"full-fledged"
In a full manner; without lack or defect.
"The newly installed solar panels are fully functional and ready to power the entire house."
In plain English: Fully means completely or totally without any part left out.
"The sun was fully up by the time we arrived at the beach."
Usage: Use fully to indicate that something has been completed entirely or possesses all necessary parts, such as charging a battery completely or utilizing a resource without restriction. Avoid using it when simply meaning "very" or "extremely," as in the incorrect phrase "fully beautiful."
The word "fully" comes from the Middle English phrase fulliche, which is derived from combining the Old English adjective full with the suffix -īċe. It has been used in English since at least the 12th century to mean completely or entirely.