Yes, there are significant differences between a crown and a tiara. According to tradition, only the Queen can wear a crown, while tiaras are worn by brides, married women, or at "white-tie" events. Crowns cover the whole head in a full circle, representing absolute power and monarchy in royal and state ceremonies, whereas tiaras are a semi-circle and cover only half the head, embodying femininity and grace, suitable for formal events. Crowns are generally larger and taller than tiaras. Additionally, both crowns and tiaras can hold cryptic meanings in the British Royal Family's context. A diadem is a type of crown or headband used in ancient times to signify the legitimacy of a ruler's reign.