A demonstrative is a word such as “this” and “that”, used to refer to a specific object, person, or entity.
In Arabic, demonstratives agree with the noun in gender, as well as number. To refer to a single masculine object, you use the word هَذا (hatha) - this. For a female object, use the word هذِهِ (hathahi) - this.
For example:
ٌٌٌٌهذا الخبزُ لذيذٌ (hatha al-khubzu lathithun) - This bread is delicious.
هذه التفاحةُ حلوٌ (hathahi al-tuffahatu hulwun) - This apple is sweet.
Both of the above sentences are nominal sentences, with words in the nominative case with a damma (”u”) or double damma (”un”) ending. The demonstrative makes the words “apple” and “bread” definite.
To refer to an object that is far, you would use say “that” instead of “this. In Arabic, the word ذلِكَ (thalika) is used with masculine objects, and تِلكَ (tilka) is used with feminine objects.