A subject ie a definite noun with “ال” may be preceded in a sentence by a demonstrative pronoun as I explained in this post. But while a demonstrative pronoun may not always be written before a definite noun in a sentence, it could also be singly used as a subject.

These are shown below:

The Arabic subjects without a demonstrative pronoun

The subject in each of the sentences above is written without a demonstrative pronoun while the ones below illustrate the use of the demonstrative pronouns alone as a subject.

An Arabic demonstrative pronoun could be singly used as a subject