Know your English: Meaning of 'sting operation'; difference between 'while' and 'whilst'; 'psephologist'; 'to hit the sack'

What happened: meanings and usage notes for four English items

A language-explainer clarified meanings and usage for four items: sting operation, while vs whilst, psephologist, and the idiom to hit the sack (meaning ‘go to bed’).

1) ‘Sting operation’: planned law-enforcement entrapment (often undercover)

A sting operation is a planned law-enforcement scheme designed to entrap a criminal, typically involving undercover work. In informal speech, sting can also mean to cheat or to overcharge.

2) ‘While’ vs ‘Whilst’: same meaning; ‘whilst’ is mainly British English