/ ˌdɪmɪˈnjuːʃn; NAmE -ˈnuːʃn/ noun diminution (of / in sth) ( formal )
1.
[ U ] the act of reducing sth or of being reduced :
the diminution of political power
2.
[ C , usually sing. ] a reduction; an amount reduced :
a diminution in population growth
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WORD ORIGIN
Middle English : via Old French from Latin deminutio(n-) , from the verb deminuere , from minuere make small.