Pensive means deep in thought, and a little sad. A pensive mood, look pensive, pensive and quiet.
The sadness is what separates it from thoughtful, and it is usually read from a face rather than reported by the person. The French behind it is simply to think, so the melancholy was added by English.
1adjectivepensiveDeep in thought, and a little sad.
“She sat by the window in a pensive mood, watching the rain.”
pensive is a quality.
Old French pensif comes from penser, to think, from Latin pensare, to weigh.
Proto-Indo-European
*(s)pend-
Latin
pēnsō
Old French
pensif — thoughtful
Middle English
pensif
English, today
pensive
Built from
From Middle English pensif, pensyfe, pencyve, from Old French pensif (“thoughtful”), from penser (“to think”) (from Latin pēnsō) + -if (English -ive).
Etymology from Wiktionary, CC BY-SA