Evidentiality and information source

Every language has an array of ways of referring to information source. This may be accomplished with verbs referring to reports, claims, or opinions, with adverbs, with parentheticals, prepositional phrases or with particles. In about one quarter of the world?s languages, marking information source is obligatory. These languages have a grammatical category of evidentiality. Other languages have evidential extensions of non-evidential categories–such as conditional in French, perfect in Georgian and participles in Lithuanian. Just like non-grammatical expressions of information source, evidential extensions of non-evidential categories (known as evidential strategies) share the evidential meanings and not infrequently give rise to grammatical evidentials. The term ?evidential? primarily relates to information source as a closed grammatical system whose use is obligatory. The term ?information source? relates to the corresponding conceptual category. This is akin to the distinction between the category of ?tense?, as grammaticalized location in time, and the concept of ?time?. Expressions related to information source are heterogeneous and versatile. They include closed classes of particles and modal verbs, and an open-ended array of verbs of opinion and belief. The term ?lexical evidentiality? is misleading in that it obscures these vital differences. Extra-grammatical ways of marking information source may allow more detailed specification of various degrees of assumption, inference, opinion than do grammatical evidential systems, and often reliability, and speaker?s evaluation of information