/ əˈsɜːʃn; NAmE əˈsɜːrʃn/ noun
1.
[ C ] a statement saying that you strongly believe sth to be true
SYN claim :
He was correct in his assertion that the minister had been lying.
Do you have any evidence to support your assertions?
➡ note at claim
2.
[ U , C ] the act of stating, using or claiming sth strongly :
the assertion of his authority
The demonstration was an assertion of the right to peaceful protest.
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WORD ORIGIN
late Middle English : from Latin assertio(n-) , from the verb asserere claim, affirm, from ad- to + serere to join.