to make (something) known formally or explicitly
to make (something) evident; to show
to state (something) emphatically; to affirm
They declared their innocence
to make a full statement of (income or property subject to tax or duty)
I have nothing to declare except my genius — Oscar Wilde
to announce (e.g. a trump suit) in a card game
to announce that one has (a combination of playing cards) in canasta, rummy, etc
to make a declaration
(often + for) to make a public statement of one's support
said of a cricket captain or team: to announce a decision to end the team's innings before all the batsmen are out
declare war
to commence hostilities; specif to make a formal declaration of intention to go to war
declarable adj
declarer noun
[Middle English declaren via French from Latin declarare, from de- + clarare to make clear, from clarus clear]