1. in an official or ceremonial way
2. following established rules, procedures, or conventions
3. in a polite, serious, or dignified manner

Examples

• The president formally announced his resignation yesterday.
• Students must formally apply for graduation by the deadline.
• She was formally dressed in a black evening gown.
• The contract was formally signed by both parties.
• He formally introduced himself to the new neighbors.
• The complaint must be formally submitted in writing.
• They formally opened the new library with a ribbon-cutting ceremony.