Differences or Marks of Cadency are used in heraldry to distinguish the various branches or cadets of one family.
In order of age, the following apply:
1st son - Label
The label was a decorative piece of fabric, usually silk. It was a popular trimming for dress and decor during the Middle Ages. In heraldry, it is represented by a narrow band across the top of the shield, edged by another band from which three short bars hang down. Lately the bars have been drawn more like dovetails, like triangles inserted point first into the lower band. In English arms a label was a mark of difference indicating that the bearer was the eldest son and heir. Some labels on coats of arms can be traced to this origin.
2nd son - Crescent
The crescent stands for one who has been "enlightened and honored by the gracious aspect of his sovereign." It is also borne as a symbol of the hope of greater glory. Knights returning from the crusades introduced the crescent, the badge of Islam, into the language of heraldry. The heraldic crescent has a very deep base and curving horns that quickly sharpen to points close together. Crescents also represent the moon that lights the night sky for travelers, though it does not resemble the shape of a crescent moon very closely. In English arms it was also a mark of cadency signifying the second son. The reversed crescent is a crescent with the horns turned down. The term increscent indicates a crescent with the horns facing the observerís left, and decrescent is a crescent facing the observerís right.
3rd son - Mullet (five pointed star)
The star symbolizes honor, achievement and hope. Stars with wavy points are emblems of God's goodness, or some other eminence that elevated the first bearer above the common people. Stars, estoiles and mullets are often confused because of their similarity, which is not helped by the fact that no definite lines have ever officially been followed regarding their specific differences. In England stars with wavy rays are called estoiles, when they are straight they are called mullets, and technically there is no such thing as a star. A mullet has five points unless another number is specified, which it often is, but an estoile can have any number so one must be provided. However, in Scotland the distinction between a mullet and a star is that a mullet is pierced, which actually makes it a spur-revel, and a star is whole. In France the definition of a mullet is different yet again; this time, it has no less than six points.
4th son - Martlet
The martlet, or heraldic swallow, is a bird perceived as swift and elegant and is a device for someone prompt and ready in the dispatch of his business. It may also represent one who has to subsist on the wings of his virtue and merit alone. The martlet signifies nobility acquired through bravery, prowess or intelligence. On English arms it was a mark of cadency signifying the fourth son, for whom there was little doubt that there would be no land left for him to inherit. Interestingly, this heraldic symbol was a perpetuation of the popular belief that the swallow has no feet. This is supported by the fact that one never does see swallow standing, but regardless, the martlet is consistently drawn without feet. If the feet are drawn the symbol becomes a swallow, which is less common than the martlet. The swallow is a vanguard of spring and represents a bearer of good news.
5th son - Annulet
The annulet is a plain ring. As a closed circle, it is symbolic of continuity and wholeness. The Romans are said to have worn a ring as a sign of knighthood and rings are still used at some coronations and in the institution of knighthood. The annulet may have been borne to indicate that the bearer had the superior qualities of a knight. In some circles an annulet represented riches.
6th son - Fleur de lis
The fleur-de-lis is a very ancient and widely used symbol. It is found in East Indian, Egyptian and Etruscan decorations, as well as Roman and Gothic architecture. It may originally have been intended to represent a lily or white iris, or an arrow or spearhead. In Christian symbolism, the fleur-de-lis is used as a symbol of the Holy Trinity and as an ensign of the Virgin Mary. In heraldry, it is also said to signify faith, wisdom, and valor. Fleurs-de-lis are now most commonly associated with France. In ancient times they may have signified a connection with that country through war, marriage or property rights.
7th son - Rose
The rose is a symbol of hope and joy; it is first among flowers and expresses beauty and grace. With a red blossom, it is a symbol of martyrdom. The white rose expresses love and faith and in Christian symbolism, it signifies purity. The yellow rose is a symbol of absolute achievement. The conventional form of a heraldic rose has five displayed petals that mimic the look of a wild rose on a hedgerow. The famous Wars of Roses, between the red rose of the house of Lancaster and the white rose of the house of York, ended after the succession of the Tudors to the throne. After this the heraldic rose developed a double row of petals which was obviously in effort to combine the rival emblems, although the element of increasing familiarity with the cultivated rose was also present. During the reign of the Tudors there was a more naturalistic trend in heraldry, and stems and leaves were added to the rose. Nevertheless, heraldry has accomplished what horticulture could not, and roses will be found tinted blue, black and green, in addition to more natural colours.
8th son - Cross Moline
The cross moline is a simple cross with the ends of the arms split and curved away from each other to either side. If they curve so much that they actually curl under the cross is often described as a cross anchory. A cross moline with rectangular split ends is also known as the "miller's cross" or "cross miller," which is supposed to represent a millrind.
9th son - Double Quatrefoil
Quatrefoils are not the same as shamrocks, though they do have four leaves; the leaves of a quatrefoil are more circular and they appear without the stem of a trefoil, except for very rarely. Architects placed this symbol on churches to signify that the gospel, the harbinger of peace and immortality, was preached there. In British rules of inheritance, the double quatrefoil signified the ninth son.