The formal term for painkillers is analgesics, a word derived from the Greek words an (without) and algia (pain). The three most commonly used types of pain medicine today are the nonsteroidal anti-inflammatory drugs (NSAIDs), the paracetamol based drugs and the opioid drugs.

The nonsteroidal anti-inflammatory drug (NSAIDs) group contains a wide range of different painkillers. Examples of commonly known NSAID painkillers are Aspirin, Diclofenac and Ibuprofen. NSAID pain killers do not only alleviate pain; they will also lower fever and decrease inflammations. They are called non-steroidal in order to discern them from the steroids, since the steroids are also used for their anti-inflammatory capacity. Aspirin was discovered in 1829 when salicylic acid was chemically isolated for the first time, but willow bark containing salicylic acid has been used as a pain killer long before the 19th century. A lot of NSAIDs are available over-the-counter but this does not mean that they are harmless. When misused, even comparatively weak NSAIDs can have severe side effects, including bleeding ulcers and photosensitivity. NSAIDs are generally not recommended during pregnancy.

Paracetamol is also known as acetaminophen. Both words are derived from the chemical name for this painkilling compound: N-acetyl-para-aminophenol and para-acetyl-amino-phenol. Two examples of commonly known brand names under which Paracetamol is marketed are Tylenol and Panadol. Painkillers containing Paracetamol will relieve pain and decrease a fever, but unlike the NSAID painkillers they have no anti-inflammatory properties. One of the advantages of Paracetamol compared to NSAIDs is that Paracetamol painkillers will not affect the blood