Etymology and Classification of Pain
- Pain first attested in English in 1297, derived from Old French 'peine' and Latin 'poena'
- Pain also means torment, hardship, suffering in Late Latin and Greek
- Recommended features to describe a patient's pain: region, system, duration, intensity, cause
- Helps identify specific characteristics, determine treatment options, and improve communication
- Enables accurate diagnosis and management of pain conditions

Chronic versus Acute Pain
- Pain is usually transitory but can persist for years in some conditions
- Chronic pain lasts a long time, while acute pain resolves quickly
- Distinction based on duration, with varying definitions

Types of Pain
- Allodynia: pain in response to a normally painless stimulus
- Phantom pain: felt in amputated or disconnected body parts
- Causes of pain: abnormalities in the nervous system, nerve damage, spinal cord injury, diabetes, leprosy
- Functional effects of pain: impairments in attention, memory, problem-solving, information processing
- Negative emotions associated with pain: increased depression, anxiety, fear, anger

Theories and Understanding of Pain
- Historical theories proposed by ancient Greeks, Avicenna, Descartes
- Modern understanding: differentiation between noxious and non-noxious stimuli, nociceptors, pain signaling pathways

Evolutionary and Behavioral Role of Pain
- Pain is part of the body's defense system and serves as a warning signal
- Congenital insensitivity to pain reduces life expectancy
- Pain may be shaped by natural selection as a signal for relief and care
- Idiopathic pain may be an exception to pain's helpfulness for survival
- Pain thresholds: pain perception, pain threshold intensity, pain tolerance
- Assessment of pain: self-report, healthcare professionals' perception, pain intensity scales, multidimensional pain inventory
- Assessing pain in non-verbal individuals: observation of behaviors, changes in routine, crying in infants