Deixis
The deictic element indicates whether or not a specific subset of a noun is intended; and if so, which subset. A deictic is either (i) specific or (ii) non-specific. The specific deictics are given in the following table.
determinative interrogative
demonstrative this, these; that, those; the which(ever); what(ever)
possessive my, your, our, his, her, its, their, one's, [John's] [my father's], etc. whose(ever), [which person's] etc.

The subset in question is specified by one of two possible deictic features: either

* (a) demonstratively, i.e., by reference to some kind of proximity to the speaker
o ("this", "these" = "near me"; "that", "those" = "not near me"), or
* (b) by possession, i.e., by reference to 'person' as defined from the standpoint of the speaker
o ("my", "your", "our", "his", "her", "its", "their"; also "Mary's", "my father's", etc.)

together with the possibility of an interrogative in both of these categories (demonstrative "which?" and possessive "whose?"). All of these have the function of identifying a particular subset of the noun that is being referred to.

"Proximity to the speaker" refers not only to physical distance, but also to temporal; deictics orient the listener to the 'speaker-now', the temporal–modal complex that constitutes the point of reference of the speech event. So, "this tragedy" refers to one that is current or recent and/or is or was geographically close to the speaker, whereas "that tragedy" refers to one that occurred in the past and/or was less geographically close.

There is one more item in this class, namely "the". The word "the" is a specific, determinative deictic of a peculiar kind: it means "the subset in question is identifiable; but this will not tell you how to identify it—the information is somewhere around, where you can recover it"; typically, the listener/reader can recover the information from assumed general knowledge, the specific context, or from a specific and recent point in the text. So whereas "this train" means "you know which train: the one near me", and "my train" means "you know which train: the one I own", "the train" means simply "you know which train." Hence "the" is usually accompanied by some other element that supplies the information required: for example, "the long train" means "you know which train: you can tell it by its length."

Non-specific deictics convey the sense of all, or none, or some unspecified subset. The main categories and main items in each are as follow.

(a) Total

* positive ("each", "every", "both", "all")
* negative ("neither", "no", i.e. "not any")

(b) Partial

* selective ("one", "either", "some", "any")
* non-selective ("a" or "an", "one")

There are two systems of number for English nouns, one associated with each of the two kinds of deictics. (i) With specific deictics, the number system is non-plural versus plural; mass nouns are grouped together with singular, in a category of non-plural. So "this" and "that" go with non-plural (singular or mass), and "these" and "those" go with plural.

For example, for non-plural nouns, singular might be "this train" (plural "these trains") and mass might be "this electricity" (no plural equivalent).

(ii) With non-specific deictics, the system is singular versus non-singular. So "a" and "an" go with singular, and weak "some" with non-singular (mass or plural).

For example, "a train" is singular (plural "trains" or "some trains"); non-singular mass ("electricity" or "some electricity" has no singular equivalent).

If there is no deictic element, the noun is non-specific and, within that, non-singular. In other words, a noun may have no deictic element in its structure, but this does not mean that it has no value in the deictic "system", but simply that the value selected is realized by a form having no deictic in the expression.