Synonyms of the word

black-tie

• adj. Moderately formal; usually requiring a dinner jacket (tuxedo) for men.

formal

• adj. Being in accord with established forms.
• adj. Official.
• adj. Relating to the form or structure of something.
• adj. Relating to formation.
• adj. Ceremonial or traditional.
• adj. Proper, according to strict etiquette; not casual.
• adj. Organized; well-structured and planned.
• adj. (mathematics) Relating to mere manipulation and construction of strings of symbols, without regard to…
• n. Formalin.
• n. An evening gown.
• n. An event with a formal dress code.

semiformal

• adj. Somewhat formal.