هَذَا and أَنَا are also definite, but they are not proper names.
هَذَا كِتَابٌ — This is a book. هَذَا is an indeclinable demonstrative in the nominative position as mubtadaʾ; كِتَابٌ is a nominative predicate.
Indeclinable (mabnī) must not be confused with a diptote (ghayr munṣarif): the latter remains an inflected noun.
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Definiteness and Proper-Name Status in Diptote Rules
هَذَا and أَنَا are also definite, but they are not proper names.
هَذَا كِتَابٌ — This is a book. هَذَا is an indeclinable demonstrative in the nominative position as mubtadaʾ; كِتَابٌ is a nominative predicate.
Indeclinable (mabnī) must not be confused with a diptote (ghayr munṣarif): the latter remains an inflected noun.