In classical heraldry, vert is the name of the tincture roughly equivalent to the colour "green". It is one of the five dark tinctures (colours). The word vert is simply the French for "green". It is used in English in the sense of a heraldic tincture since the early 16th century. In Modern French, vert is not used as a heraldic term. Instead, the French heraldic term for green tincture is sinople. This has been the case since ca. the 16th century. In medieval French heraldry, vert also meant "green" while sinople was a shade of red. Vert is portrayed by the conventions of heraldic "hatching" (in black and white engravings) by lines at a 45-degree angle from upper left to lower right, or indicated by the abbreviation vt. when a coat of arms is "tricked".
The colour green is commonly found in modern flags and coat of arms, and to a lesser extent also in the classical heraldry of the Late Middle Ages and the Early Modern period. Green flags were historically carried by the Fatimid Caliphate in the 10th to 12th centuries, and by Ottokar II of Bohemia in the 13th century. In the modern period, a Green Ensign was flown by Irish vessels, becoming a symbol of Irish nationalism in the 19th and 20th century. The Empire of Brazil used a yellow rhombus on a green field from 1822, now seen in the flag of Brazil. In the 20th century, a green field was chosen for a number of national flag designs, especially in the Arab and Muslim world because of the symbolism of green in Islam, including the solid green flag of the Libyan Arab Jamahiriya (1977).