Contact angles and wettability: towards common and accurate terminology

Much interest has recently been focused on contact angles, wetting and non-wettable surfaces as is evidenced by the rapid pace and sheer number of papers published in recent years. However, in many cases there exist misconceptions and misuses of terminology, leading to misinterpretation of experimental contact angles, measurements of which deceptively appear to be simple. Terms describing contact angles, wettability, superhydrophobicity and similar other terminology are loosely used. In this contribution, key terms used in relation to contact angles are defined precisely based on the accumulative knowledge from the surface chemistry community over the last decades. The definitions provided are scientifically rigorous to avoid any ambiguity and confusion. The theoretical considerations underlying these definitions are only briefly mentioned, with references to the relevant papers. Interpretation and meaning of the measured contact angles can be made simpler if the basic concepts are clearly understood and theory-based indications are applied. The clarity of definitions should make data interpretation and comparison easier for future contributions to journals, including this journal.