The root would likely be "pense," which means to pay over or give someone or something its fair value, as in the English words, compensate - to pay what is justly due, and recompense - to repay for harm done. Further, we see it slightly changed in the British "Pence," a monetary unit, which is, of course, used to pay for things. So pensive, meaning now deep in thought, would have had basically the same meaning at its origin as it does now, just phrased differently - to pay full attention to some matter, in this case with one's mind.
As the sun set over the ocean, Emily sat on the beach, lost in pensive thoughts about her future.
The detective stood staring at the opaque window, looking pensive.
I can see why the word thoughtless might seem to be an antonym for pensive, since a pensive person thinks a lot and a thoughtless person doesn't, however, thoughtlessness is really about irresponsibility, it is not really about thought in general. The opposite of thoughtless is thoughtful or responsible, not pensive. The opposite of pensive would be spontaneous, or glib.
She sat with a pensive, faraway look on her pretty face, absorbed with thoughts of their last night together.
Thoughtful, reflective, contemplative.
pensive
Sianna is a modern feminine name of American origin. It does not have a specific meaning as it is a contemporary invented name.
Thoughtful, sober, or sad; employed in serious reflection; given to, or favorable to, earnest or melancholy musing., Expressing or suggesting thoughtfulness with sadness; as, pensive numbers.
Thoughtful, sober, or sad; employed in serious reflection; given to, or favorable to, earnest or melancholy musing., Expressing or suggesting thoughtfulness with sadness; as, pensive numbers.
pensive = gânditor
Superlative of remote: remotest; comparative of remote: more remote. Superlative of painful: most painful; comparative of painful: more painful. Superlative of pensive: most pensive; comparative of pensive: more pensive.
"He was pensive most days, scornful others." Pensive means dreamily or wistfully thoughtful.
Pensive maens deep in thought. Edwad is pensive when he reads people's minds.
Many people are pensive during tests. His essay when read made you pensive.
France as it is at this time, is contemporary
he was sitting on the sofa in a pensive way, he couldn't stop thinking of her not being here any more
As the sun set over the ocean, Emily sat on the beach, lost in pensive thoughts about her future.