Definition
A scheme is a structured plan — an organized arrangement of parts designed to reach a goal. From the Greek skhema, 'form' or 'figure,' it can be neutral or even official (a pension scheme, a colour scheme, a classification scheme), or it can darken into a cunning plot, as in 'a scheme to defraud investors.' British English leans on the neutral, systematic sense; American English hears the sly one more readily. At its core the word means design with intent: pieces deliberately laid out to produce an effect.
Examples
Collocations
a pension scheme·a colour scheme·hatch a scheme·a classification scheme·a scheme to
Synonyms
plan·system·design·blueprint·plot
Word family
scheming (adjective)·schemer (noun)·schematic (adjective)
In TOEFL & IELTS
Watch the transatlantic split: in British English a scheme is usually a neutral organized plan (a 'recycling scheme', a 'pension scheme'), while in American English it often implies a deceitful plot. TOEFL/IELTS reading passages use both, so read for tone. Useful collocations: launch / introduce / devise a scheme; a colour / classification scheme. The adjective schematic ('a schematic diagram') appears in technical writing.