The doctrine of signatures refers to two separate concepts. The first has an occult meaning, in which the arrangement of magical signatures is thought to have certain powers.

The second meaning is an ancient European philosophy that held that plants bearing parts that resembled human body parts, animals, or other objects, had useful relevancy to those parts, animals or objects. It could also refer to the environments or specific sites in which plants grew. Many of the plants that were so regarded today still carry the word root "wort", an Anglo-Saxon word meaning herb, as part of their modern name.

Some "wort" plants:

• Lousewort , Pedicularis - thought to be useful in repelling lice
• Spleenwort, Asplenium - thought to be useful in treating the spleen
• Liverwort - thought to be useful in treating the liver
• Toothwort, Dentaria - thought to be useful in treating tooth ailments