Bonnet has been used as the name for a wide variety of headgear for both sexes—more often female—from the Middle Ages to the present. As with "hat" and "cap", it is impossible to generalize as to the styles for which the word has been used, but there is for both sexes a tendency to use the word for styles in soft material and lacking a brim, or at least one all the way round, rather than just at the front. Yet the term has also been used, for example, for steel helmets. This was from Scotland, where the term has long been especially popular.

Headgear, headwear, or headdress is any element of clothing which is worn on one's head, including hats, helmets, turbans and many other types. Headgear is worn for many purposes, including protection against the elements, decoration, or for religious or cultural reasons, including social conventions.