difference between semi formal and formal dress The Girlfriend's Guide to Cocktail Attire: A semi-formal code for evening events, weddings, upscale gatherings. Think: dressy but not stuffy. Cocktail attire has fewer rules than Black Tie and White Cocktail or Semiformal - Wedding

V-Neck can also be adjusted wider or more narrow depending on the look you want

Mermaid dresses follow the figure before flaring near the knee, while sheath and column gowns create a straighter, more streamlined look

To complete the ensemble, accessorize with beach-inspired jewelry and comfortable sandals for a seamless transition from ceremony to seaside reception

but there are several additional insignia for specialty communities (example: SEALS) Neckerchief / Tie Next we have the neckerchief / tie

Keep your knitwear slim-fitting and high-quality

If the bride says it is ok and as long as it doesnt clash with the bridal party, I think a long dress is very appropriate to wear to a wedding