Complex sentence: A roundel in is a circular disc used as a symbol; the term is used in heraldry but also commonly used to refer to a type of national insignia used on military aircraft, generally circular in shape and usually comprising concentric rings of different colours.
Split into simpler sentences: A roundel in is a circular disc used as a symbol. The term is used in heraldry but also commonly used to refer to a type of national insignia used on military aircraft, generally circular in shape and usually comprising concentric rings of different colours.