For simple present tense:
* ay: This is the most common and versatile form of "is." It can be used for both singular and plural subjects.
* 'y: This is a shortened form of "ay" and is used in certain grammatical structures.
For past tense:
* ay: This is also used for past tense, but it usually requires a helping verb like "na" or "nang."
* nag: This is used for past tense actions.
For future tense:
* ay: This can be used for future tense with a helping verb like "mag," "mang," or "ma."
Examples:
* Ang aso ay malaki. (The dog is big.)
* Siya 'y maganda. (She is beautiful.)
* Ang libro ay nasa mesa. (The book is on the table.)
* Siya ay nagpunta sa paaralan. (She went to school.)
* Sila ay magsisimba bukas. (They will go to church tomorrow.)
It's important to note that Tagalog grammar is complex and there are many nuances. The best way to learn how to use "is" correctly is to practice with native speakers or consult a grammar book.