Words to ponder

I like words. I like to look them up in the dictionary and write their definitions in a notebook I have designated for good words. Oftentimes, while I go about my tedious housework, or the never-ending gardening, I ponder on words.
It seems there is some confusion about obligation, responsibility and duty.
Duty is dictated by one's conscience.
Obligation refers to what one is bound to do to fulfill a particular contract, promise or social requirement.
Responsibilty refers to a particular task for which one is accountable or answerable.
Nowhere is this more confusing than from a parent's perspective, where all three merge, becoming almost indistinguishable from one another. It's difficult to separate obligation from responsibility, easy to confuse them with duty.
Perhaps on a larger scale, we all forget which is which from time to time. Is it our obligation, our responsibilty, or our duty to do the things we do?