Fully means completely, with nothing left out. Fully booked, fully aware, fully recovered.
It is the adverb of full and is used far more with participles and adjectives than with verbs: fully qualified, fully automatic, fully understand. Several combinations are practically fixed — fully fledged, fully paid up, fully grown. It often carries a note of reassurance in official language: fully compliant, fully insured. Note not fully, which is a common polite way of saying no, and that fully is stronger than very and weaker than nothing at all.
1adverbfullyCompletely, with nothing left out.
“She was fully aware of what it would cost.”
2adverbamountAt least, of an amount, said for emphasis.
“Fully half the audience had left by then.”
Too few real examples of this word to estimate which sense is commonest.
fully is a degree of completeness.
Also accepted in games: entirely
Old English
fullīċe — fully
Middle English
fully
English, today
fully
From Middle English fully, fulliche, volliche, from Old English fullīċe (“fully”), equivalent to full + -ly. Compare German völlig (“fully”), Swedish fullt (“fully”).
Etymology from Wiktionary, CC BY-SA