In this study definiteness is considered in view of information structures, especially giving weight to the notion of "familiarity." We compare it with three other information structures: old- and new-information, theme and rheme, and reference. Through this comparison we find that the category of definiteness is independent from the other structures, although it correlates with them.

a) Old- and new-information is "already activated" and "unactivated" information in certain discourse but definiteness depends on a writer/speaker's assumptions.
b) Theme-rheme structure is strategy on the sentence level though definiteness is on the noun phrase level.
c) Referentiality means how a noun phrase refers (or does not refer) to an entity, though definiteness is the relation between a noun phrase and what it refers to.

Then, this paper analyses the Egyptian short play "cArafa Kayfa Yamuutu" by Tawfiiq al-Hakiim to show how definite noun phrases are used in discourse, and we found that the following features decide the usage of definite noun phrases:

1) how much the speaker feels convinced of an issue, and
2) how much the speaker puts importance on the object.

The result tells us that the structure of definiteness and indefiniteness is not only defined through hearersﾕ or readersﾕ state, but also that definiteness can be employed actively or subjectively by the speaker/writer. Definiteness is one independent information structure and a device which can be used actively by writers/speakers to send their message to others.

(The paper itself is written in Japanese.)