 Reference is concerned with designating things, activities, properties, relationships etc. in the outside world by linguistic means. The following types of reference can be distinguished, definite, indefinite and generic reference. Definite reference is an act of identifying entities through linguistic expressions. In this example the noun phrase the doctor can be uniquely identified by the speaker and the listener. The set of definite referring expressions in present-day English includes definite determiners, personal pronouns, proper names and certain locative and temporal adverbs. In instances of indefinite reference only the features of the class to which the reference belongs are relevant. Here is our example again with a tiny but important difference. The noun phrase a doctor is not necessarily identifiable neither by the speaker nor the hearer. In fact to understand the speaker the hearer does not have to know which doctor is involved. Indefiniteness is signaled in present-day English by indefinite determiners, indefinite pronouns and certain locative and temporal adverbs. There are instances where potentially referring elements such as nouns do not pick out a particular entity but refer to a class of reference. This is called generic reference. These three sentences have readings which involve generic reference. Each of them states that being of great use is a general characteristic of the members of the class of computers. In summary the term reference labels the activity of picking out precise things or reference in the world on some specific occasion. It establishes a relationship between words or more precisely like seems and real world entities.