Assert, v. t. [imp. & p. p. Asserted; p. pr. & vb. n. Asserting.]
Etymology: [L. assertus, p. p. of asserere to join or fasten to one's self, claim, maintain; ad + serere to join or bind together. See Series.]
1. To affirm; to declare with assurance, or plainly and strongly; to state positively; to aver; to asseverate. Nothing is more shameful . . . than to assert anything to be done without a cause. Ray.
2. To maintain; to defend. [Obs. or Archaic] That . . . I may assert Eternal Providence, And justify the ways of God to men. Milton. I will assert it from the scandal. Jer. Taylor.
3. To maintain or defend, as a cause or a claim, by words or measures; to vindicate a claim or title to; as, to assert our rights and liberties. To assert one's self, to claim or vindicate one's rights or position; to demand recognition.
Syn. -- To affirm; aver; asseverate; maintain; protest; pronounce; declare; vindicate. -- To Assert, Affirm, Maintain, Vindicate. To assert is to fasten to one's self, and hence to claim. It is, therefore, adversative in its nature. We assert our rights and privileges, or the cause of tree institutions, as against opposition or denial. To affirm is to declare as true. We assert boldly; we affirm positively. To maintain is to uphold, and insist upon with earnestness, whatever we have once asserted; as, to maintain one's cause, to maintain an argument, to maintain the ground we have taken. To vindicate is to use language and measures of the strongest kind, in defense of ourselves and those for whom we act. We maintain our assertions by adducing proofs, facts, or arguments; we are ready to vindicate our rights or interests by the utmost exertion of our powers.
Shades of meaning
Fernald has no entry of its own for assert; he lists it under allege, state.
Where he writes about it:
The accused will usually assert his innocence. — from allege
Assert (L. ad, to, and sero, bind) is strongly personal, signifying to state boldly and positively what the one making the statement has not attempted and may not attempt to prove. — from state
Affirm has less of egotism than assert (as seen in the word self-assertion), coming nearer to aver. — from state
It has more solemnity than declare, and more composure and dignity than asseverate, which is to assert excitedly. — from state
Assert is combative; assure is conciliatory. — from state
I assert my right to cross the river; I assure my friend it is perfectly safe. — from state
One may assert himself, or assert his right to what he is willing to contend for; or he may assert in discussion what he is ready to maintain by argument or evidence. — from state
To assert without proof is always to lay oneself open to the suspicion of having no proof to offer, and seems to arrogate too much to one's personal authority, and hence in such cases both the verb assert and its noun assertion have an unfavorable sense; we say a mere assertion, a bare assertion, his unsupported assertion; he asserted his innocence has less force than he affirmed or maintained his innocence. — from state