Bold (noun) – type of print where words or letters appear in thick, dark characters. This style is often used to highlight or emphasize text in written or printed materials.
Headwords in dictionaries are usually printed in bold to make them stand out from the rest of the text.
“Headwords are printed in bold.”
From Old English bald, of Germanic origin. The word is historically associated with brightness and strength, reflecting its visual clarity on a printed page.
Author’s summary: The noun “bold” refers to thick, dark print used for emphasis, derived from Old English bald meaning bright or strong.