1. to say something in a serious or official way
2. to officially tell customs officers about goods or money when entering a country
3. to say that you support a particular person or idea

Examples

• The president declares a national emergency.
• She declares her love for him in the letter.
• You must declare all income on your tax return.
• The judge declares the defendant guilty.
• He declares his intention to run for office.
• Travelers must declare expensive items at customs.
• The company declares bankruptcy after losing money.