An alkaloid is a naturally occurring compound that primarily contains basic nitrogen atoms. These compounds are often found in plants and can have significant effects on humans and animals. Alkaloids are known for their pharmacological properties, which can include pain relief, stimulation, or even toxicity. Common examples of alkaloids include caffeine, morphine, and nicotine. Alkaloids are classified into various categories based on their chemical structure and effects. They play essential roles in plant defense mechanisms, deterring herbivores and attracting pollinators. Due to their potent biological activities, alkaloids are widely studied in the fields of medicine and pharmacology for their potential therapeutic applications.