different, with "now" referring to the moment the sentence is written and "when" referring to the moment the sentence is read. Tenses are generally separated into absolute (deictic) and relative tenses. So, for example, simple English past tense is absolute, such as in: He went. whereas the pluperfect is relative to some other deictically specified time, as in: He had gone. Other categories Though the traditional categories of deixis are perhaps the most obvious, there are other types of deixis that are similarly pervasive in language use. These categories of deixis were first discussed by Fillmore and Lyons, and were echoed in works of others. Discourse deixis Discourse deixis, also referred to as text deixis, refers to the use of expressions within an utterance to refer to parts of the discourse that contain the utterance—including the utterance itself. For example, in: This is a great story. "this" refers to an upcoming portion of the discourse; and in: That was an amazing account. "that" refers to a prior portion of the discourse. Distinction must be made between discourse deixis and anaphora, which is when an expression makes reference to the same referent as a prior term, as in: Matthew is an incredible athlete; he came in first in the race. In this case, "he" is not deictical because, within the above sentence, its denotative meaning of Matthew is maintained regardless of the speaker, where or when the sentence is used, etc. Lyons points out that it is possible for an expression to be both deictic and anaphoric at the same time. In his example: I was born in London, and I have lived here/there all my life. "here" or "there" function anaphorically in their reference to London, and deictically in that the choice between "here" or "there" indicates whether the speaker is or is not currently in London. The rule of thumb to distinguish the two phenomena is as follows: when an expression refers to another linguistic expression or a piece of discourse, it is discourse deictic. When that expression refers to the same item as a prior linguistic expression, it is anaphoric. Switch reference is a type of discourse deixis, and a grammatical feature found in some languages, which indicates whether the argument of one clause is the same as the argument of the previous clause. In some languages, this is done through same subject markers and different subject markers.