Simple categories matching intractable:

• infection,
• pain,
• cancer,
• disease,
• material,
• mineral,
• condition,
• component,
• illness,
• symptom,
• emotion,

Members with property intractable:

• ischemic_pain,
• phantom-limb_pain,
• cancer,
• diabetes,
• dyspnea,
• tar,
• pneumonia,
• zirconium_alloy,
• viral_hepatitis,
• lymphoma,
• tuberculosis,
• glass_sheet,
• inorganic_salt,
• leukemia,
• hepatitis,
• diorite,
• cloth,
• nausea,
• septicemia,
• alabaster,
• viral_disease,
• porphyry,
• congenital_anomaly,
• cancerous_pain,
• collagen_disease,
• advanced_cancer,
• listlessness,
• back_pain,
• immunodeficiency_disease,
• arthritis,
• malignant_tumor,
• parkinson_disease,
• rheumatoid_arthritis,
• central_pain,
• syphilis,
• neuritis,
• refractory_cancer,
• muscular_dystrophy,
• herpes,
• osteoarthritis,
• soap_suds,
• stone,
• vertigo,
• leprosy,
• schizophrenia,
• crude_petroleum,
• boredom,
• wood,
• cardiovascular_disease,
• huntington_disease,
• autoimmune_disease,
• seed,
• anger,
• tardive_dyskinesia,
• leukaemia,
• nylon_bushing,
• chronic_pain,
• vulcanized_elastomer,
• interstitial_pneumonia,
• brain_cancer,
• multiple_arthritis,
• severe_arthritis,
• lupus,
• cholera,
• cancer_pain,
• pain,
• zircon,
• chronic_bronchitis,
• pulmonary_emphysema,
• alkali,
• pancreatic_carcinoma,
• refractory_metal,
• infectious_disease,
• child_leukemia,
• marble,
• pancreatic_cancer,
• gastric_cancer,
• melanoma,
• cutaneous_candidiasis,
• alzheimers_disease,
• tumor,
• haematological_malignancy,