Patient is the semantic concept which is related to object of action, but not always conforms with it. It has no clear scientific definition but usually easy to determine from meaning. Patient is an optional argument of verb (with main one called “agent”), the receiver, target or “undergoer” of an action expressed by predicate. In majority of Indo-European languages patient matches the object of the sentence in active voice ¹⁾. However, in passive voice patient is traditionally treated as the subject of sentence ²⁾. The concept of patient is very useful in describing grammar of ergative languages.