asseveration
Concise Oxford English Dictionary © 2008 Oxford University Press:
asseveration /əˌsɛvəˈreɪʃ(ə)n/
▶noun a solemn or emphatic declaration or statement.
– derivatives
asseverate verb.
asseverate verb.
– origin C16: from L. asseveratio(n-), from asseverare, from ad- ‘to’ + severus ‘serious’.
'asseveration' also found in these Oxford entries:

