Full Idea
In cases of 'de re' modality, it is a particular thing that has the property essentially or accidentally; where the modality attaches to the proposition, it is 'de dicto' - it is the whole truth that all bachelors are unmarried that is necessary.
Clarification
'De re' means concerning the thing; 'de dicto' means concerning the statement
Gist of Idea
'De re' modality is about things themselves, 'de dicto' modality is about propositions
Source
Joseph Melia (Modality [2003], Ch.1)
Book Reference
Melia,Joseph: 'Modality' [Acumen 2003], p.2
A Reaction
This seems to me one of the most important distinctions in metaphysics (as practised by analytical philosophers, who like distinctions). The first type leads off into the ontology, the second type veers towards epistemology.
Related Idea
Idea 13810 The source of de dicto necessity is not concepts, but the actual properties of the thing [Forbes,G]