Unbroken means whole, or continuing without interruption. An unbroken record, unbroken silence, unbroken by cloud.
The second sense is the commoner: unbroken sleep, an unbroken run of wins, an unbroken line of descent. It measures continuity rather than wholeness. Of a horse, unbroken means not yet trained to be ridden. Note that the word is Old English and formed exactly as it looks.
1adjectiveunbrokenContinuing without interruption.
“We had a week of unbroken sunshine on holiday.”
2adjectivewholeWhole and undamaged.
“Amazingly, the vase fell off the shelf and landed unbroken on the rug.”
unbroken is a quality of wholeness or continuity.
Old English ungebrocen is un- plus broken. Break, breach and fraction come from a shared root.
Old English
unġebrocen — unbroken
Middle English
unbroken
English, today
unbroken
From Middle English unbroken, from Old English unġebrocen (“unbroken”), equivalent to un + broken. Cognate with Dutch ongebroken (“unbroken”), German Low German unbroken (“unbroken”), German ungebrochen (“unbroken”).
Etymology from Wiktionary, CC BY-SA