Thermodynamics is a branch of physics that deals with heat, work, and temperature, and their relation to energy, entropy, and the physical properties of matter and radiation. The behavior of these quantities is governed by the four laws of thermodynamics which convey a quantitative description using measurable macroscopic physical quantities, but may be explained in terms of microscopic constituents by statistical mechanics. Thermodynamics applies to a wide variety of topics in science and engineering, especially physical chemistry, biochemistry, chemical engineering and mechanical engineering, but also in other complex fields such as meteorology.

भौतिकी में उष्मागतिकी के अन्तर्गत ऊर्जा का कार्य और उष्मा में रूपान्तरण, तथा इसका तापमान और दाब जैसे स्थूल चरों से सम्बन्ध का अध्ययन किया जाता है। इसमें ताप, दाब तथा आयतन का सम्बन्ध भी समझा जाता है।