Normal boiling point refers to the temperature at which a liquid boils under normal atmospheric pressure, which is usually 1 atm or 760 mmHg. There are several synonyms for this term, including standard boiling point, atmospheric boiling point, and normal atmospheric boiling point. These terms all refer to the same concept of the temperature at which a liquid will boil at standard pressure. In contrast, the term "critical temperature" represents the temperature at which a substance can no longer exist as a liquid, even at high pressure. Understanding these terms is essential for scientists and engineers who work with liquids or gases with specific physical properties and for individuals who want to understand the principles of chemistry and physics.