diminish

Concise Oxford English Dictionary © 2008 Oxford University Press:
diminish/dɪˈmɪnɪʃ/

▶verb

• 1 make or become less.

• 2 (as adj. diminished) Music denoting an interval which is one semitone less than the corresponding minor or perfect interval.

– phrases
(the law of) diminishing returns the principle that as expenditure or investment increases each further increase produces a proportionately smaller return.

– derivatives
diminishable adjective.

– origin ME: blend of archaic minish ‘diminish’ (based on L. minutia ‘smallness’) and obs. diminue ‘speak disparagingly’ (based on L. deminuere ‘lessen’).