1. As a definite article "the":
* Ang: This is the most common way to say "the".
* Example: Ang libro (The book)
2. As an indefinite article "a" or "an":
* Isang: This is used for singular, countable nouns.
* Example: Isang mansanas (An apple)
* Isang can also be used to express "one"
* Example: Isang araw (One day)
3. As part of a compound word:
* Sometimes, "a" is integrated into a Tagalog word.
* Example: Araw (sun/day) - This is a compound word from "a-raw"
Important Note: There is no direct equivalent for the indefinite article "a" in Tagalog, but "Isang" covers most situations.