Active pharmaceutical ingredients (APIs) may exist in various solid forms, which can lead to differences in the intermolecular interactions, affecting the internal energy and enthalpy, and the degree of disorder, affecting the entropy. Differences in solid forms often lead to differences in thermodynamic parameters and physicochemical properties for example solubility, dissolution rate, stability and mechanical properties of APIs and excipients. Hence, solid forms of APIs play a vital role in drug discovery and development in the context of optimization of bioavailability, filing intellectual property rights and developing suitable manufacturing methods. In this review, the fundamental characteristics and trends observed for pharmaceutical hydrates, solvates and amorphous forms are presented, with special emphasis, due to their relative abundance, on pharmaceutical hydrates with single and two-component (i.e. cocrystal) host molecules.

活性药物成分（API）可能以各种固体形式存在，这可能导致分子间相互作用的差异，从而影响内部能量和焓，以及紊乱程度，从而影响熵。固体形式的差异通常会导致热力学参数和理化性质的差异，例如API和赋形剂的溶解度，溶解速率，稳定性和机械性质。因此，在优化生物利用度，申请知识产权和开发合适的制造方法的背景下，API的固体形式在药物发现和开发中起着至关重要的作用。在这篇综述中，由于其相对丰富，特别介绍了药物水合物，溶剂化物和无定形形式的基本特征和趋势，