In applied linguistics and pragmatics (sub-fields of linguistics), hedges allow speakers and writers to signal caution, or probability, versus full certainty. Hedges can also allow speakers and writers to introduce or eliminate ambiguity in meaning and typicality as a category member. Hedging in category membership is used in reference to the prototype theory, to signify the extent to which items are typical or atypical members of different categories. Hedges might be used in writing, to downplay a harsh critique or a generalization, or in speaking, to lessen the impact of an utterance due to politeness constraints between a speaker and addressee. Typically, hedges are adjectives or adverbs, but can also consist of clauses such as one use of tag questions. In some cases, a hedge could be regarded as a form of euphemism. Linguists consider hedges to be tools of epistemic modality; allowing speakers and writers to signal a level of caution in making an assertion. Hedges are also used to distinguish items into multiple categories, where items can be in a certain category to an extent.