 Yet another important role of entities in the semantic structure of natural language is that of a parameter of evaluation for the truth of sentences. The standard semantic view takes a sentence to be true or false not absolutely, but relative to a time and a (possible) world. This first of all gives justice to the intuition that sentences can be true or false in actual as well as counterfactual circumstances. Moreover, there are natural language expressions that have been considered operators shifting a parameter of evaluation. Tenses and temporal adverbials are standardly taken to act as operators shifting the time of evaluation and modals as operators shifting the world of evaluation. Also conditionals are generally treated as potentially shifting the world of evaluation for antecedent and consequent.