wane

Things that wane simply grow smaller. "My initial enthusiasm for helping waned when I saw the massive pile of envelopes that needed sealing."

Things that wax and wane, like the moon, grow larger and smaller. Wax is the opposite of wane. A fad, or a fashion, or even a disease, that is on its way out the door is "on the wane." If your influence over your little brother wanes, he’ll probably stop copying you. Anything that wanes, like the moon, influence, or a feeling, has started to go away.

Definitions of wane
1

n a gradual decline (in size or strength or power or number)

Synonyms:
ebb, ebbing
Type of:
decline, diminution
change toward something smaller or lower

v grow smaller

“Interest in the project waned
Synonyms:
decline, go down
Types:
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hide 5 types...
dip
go down momentarily
wear on
pass slowly (of time)
drop
go down in value
fall off, sink, slump
fall heavily or suddenly; decline markedly
tumble
fall suddenly and sharply
Type of:
decrease, diminish, fall, lessen
decrease in size, extent, or range

v become smaller

“Interest in his novels waned
Antonyms:
climb, mount, rise, wax
go up or advance
Type of:
decrease, diminish, fall, lessen
decrease in size, extent, or range

v decrease in phase

“the moon is waning
Antonyms:
full, wax
increase in phase
Type of:
decrease, diminish, fall, lessen
decrease in size, extent, or range

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