Relationships are inherent in medicine and health. Eosinophil count normally decreases from birth to adulthood, and the risk of lung cancer increases with the amount and duration of smoking. Total leukocyte count (TLC) and hemoglobin (Hb) levels decrease up to the age of 6–8 years and show some increase thereafter in healthy subjects. Height velocity is at its peak during adolescence. Blood pressure (BP) levels have a positive relationship with waist–hip ratio (WHR), and the incidence of dental caries in children depends negatively on the socioeconomic grade of their family. Such relationships are an everyday occurrence in the practice of medicine and health, so much so that they are sometimes taken for granted.