A skull and crossbones is a symbol consisting of a human skull and two long bones crossed together under or behind the skull. The design originated in the Late Middle Ages as a symbol of death and especially as a memento mori on tombstones. Actual skulls and bones were long used to mark the entrances to Spanish cemeteries (campo santo).
In modern contexts, it is generally used as a hazard symbol, usually in regard to poisonous substances, such as deadly chemicals.
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In science, poison is one of the chemical substances that is harmful or lethal to a living organism. The term of poison is used in a wide range of scientific fields and industries, where it is often specifically defined. It may also be applied colloquially or figuratively, with a broad sense.
The symptoms and effects of poisoning in humans can mimic those of other medical conditions and vary depending on the type of poison and the system of the body affected. Common symptoms include alterations in consciousness, abnormal body temperature, irregular heart rate, and changes in respiration. The severity and specific presentation of symptoms often depend on the nature and dose of the poison involved.
Hazard symbols are universally recognized symbols designed to alert individuals to the presence of hazardous or dangerous materials, locations, or conditions. These include risks associated with electromagnetic fields, electric currents, toxic chemicals, explosive substances, and radioactive materials. Their design and use are often governed by laws and standards organizations to ensure clarity and consistency. Hazard symbols may vary in color, background, borders, or accompanying text to indicate specific dangers and levels of risk, such as toxicity classes. These symbols provide a quick, universally understandable visual warning that transcends language barriers, making them more effective than text-based warnings in many situations.