In
heraldry, a thick
diagonal band crossing a shield from upper
dexter (left as you look at it) to lower
sinister (right). In theory, but never in practice, it occupies a full third of the
field. A significantly smaller band is called a
bendlet. A bendlet that is cut off at the ends so that it doesn't reach the edge of the shield is called a
baton.
When it starts in the upper sinister and goes down to dexter it is called a bend sinister. This is sometimes said to be a mark of illegitimacy, though it is in fact no such thing. A baton sinister is sometimes used for that purpose. By a confusion with the French name barre for a bend, this may also be heard as "bar sinister", presumably because that sounds like bastard, but in English heraldry that term is nonsense, a bar being a horizontal band right across the shield, which can therefore be neither dexter nor sinister.
A field divided in half by a diagonal line is described as 'per bend' or 'party per bend'.
Smaller charges objects described as being bendwise are actually pointing diagonally in the direction of the bend, as for example the spear in Shakespeare's arms. This is in contrast to a group of objects described as in bend, which means they are individually in their normal orientation but strung out diagonally.