In heraldry

Heraldry

Heraldry is the profession, study, or art of creating, granting, and blazoning arms and ruling on questions of rank or protocol, as exercised by an officer of arms. Heraldry comes from Anglo-Norman herald, from the Germanic compound harja-waldaz, "army commander"...

, dimidiation is a method of joining two coats of arms

Coat of arms

A coat of arms is a unique heraldic design on a shield or escutcheon or on a surcoat or tabard used to cover and protect armour and to identify the wearer. Thus the term is often stated as "coat-armour", because it was anciently displayed on the front of a coat of cloth...

.

For a time, dimidiation preceded the method known as impalement

Impalement (heraldry)

In heraldry, impalement is the combination of two coats of arms side-by-side in one shield or escutcheon to denote union, most often that of a husband and wife, but also for ecclesiastical use...

. Whereas impalement involves placing the whole of both coats of arms side by side in the same shield, dimidiation involves placing the dexter

Dexter and sinister

Dexter and sinister are terms used in heraldry to refer to specific locations in an escutcheon bearing a coat of arms and by extension also to a crest. "Dexter" means to the right from the viewpoint of the bearer of the arms, to the left of that of the viewer...

 half of one coat of arms alongside the sinister

Dexter and sinister

Dexter and sinister are terms used in heraldry to refer to specific locations in an escutcheon bearing a coat of arms and by extension also to a crest. "Dexter" means to the right from the viewpoint of the bearer of the arms, to the left of that of the viewer...

 half of the other. In the case of marriage, the dexter half of the husband's arms would be placed alongside the sinister half of the wife's arms. The practice fell out of use because the result was not always aesthetically pleasing (sometimes creating strange hybrids, as seen in the examples at right), and also because in some cases, it would result in a shield that confusingly looked like one coat of arms rather than a combination of two. For instance, a bend

Bend (heraldry)

In heraldry, a bend is a coloured band running from the upper right corner of the shield to the lower left . Writers differ in how much of the field they say it covers, ranging from one-fifth up to one-third...

 combined with a bend sinister might result in a combination that simply looked like a chevron, thus hiding the fact that two coats of arms had been combined. In order to avoid these drawbacks, it became customary to use more than half of each coat of arms when combining them through dimidiation. Once this practice had begun, the logical progression was to include the whole of both coats of arms in the new shield, so that in effect, impalement replaced dimidiation as a method of combining coats of arms. One rule which carries over from dimidiation to impalement is that if a coat of arms with a bordure

Bordure

In heraldry, a bordure is a band of contrasting tincture forming a border around the edge of a shield, traditionally one-sixth as wide as the shield itself...

is impaled, the bordure does not continue down the line of impalement, but is cut short.

Sources

• Arthur Charles Fox-Davies, A Complete Guide to Heraldry (1909), pp. 182, 523-525. Online texts at http://www.archive.org/details/completeguidetoh00foxduoft or http://www7b.biglobe.ne.jp/~bprince/hr/foxdavies/index.htm .