decrease,
diminish,
lessen,
fall decrease in size, extent, or range; "The amount of homework decreased towards the end of the semester"; "The cabin pressure fell dramatically"; "her weight fell to under a hundred pounds"; "his voice fell to a whisper"
detain,
delay,
hold up cause to be slowed down or delayed; "Traffic was delayed by the bad weather"; "she delayed the work that she didn't want to perform"
retard -
slow the growth or development of; "The brain damage will retard the child's language development"
modify,
alter,
change make less severe or harsh or extreme; "please modify this letter to make it more polite"; "he modified his views on same-gender marriage"
dampen lessen in force or effect; "soften a shock"; "break a fall"
detain,
delay,
stay cause to be slowed down or delayed; "Traffic was delayed by the bad weather"; "she delayed the work that she didn't want to perform"