“Siya” is the standard and only correct spelling. In texting, where anything goes as long as it can be understood, you may encounter “sya” or even “cya”.
The traditional Pilipino alphabet (also called “abakada”) only had 20 letters. The letter “J” was not there and “dy” was what we use to imitate its sound. “Dyakpat” is the Pilipino spelling for “jackpot”, “dyanitor” for “janitor”, etc... Now with all the English letters included in the modern Filipino alphabet, it is all right to just spell them as “jackpot” and “janitor”.
We have adopted a lot of Spanish words into our vocabulary and the diphthongs “ia” and “io” are quite common in Spanish. Here are some common Tagalog words that are of Spanish origin. The syllables stressed in Tagalog are the same as the default and the indicated stresses in Spanish.
Group 1
[SPA] diario/peri
ódico (newspaper) = [TAG] dIY
Áryo/perY
Ódiko
diamante (diamond) = dIYAm
ante
dios (god) = dIY
Ós
hacienda (country estate) = asY
Enda (default stress in Spanish is on the penultimate syllable)
Group 2
democracia (democracy) = demokr
asYA
iglesia (church) = igl
esYA
desgracia (misfortune) = des/disgr
asYA (accident, misfortune)
Group 3
pacencia (patience) = pas
énsIYA
agencia (agency) = ah
énsIYA
convulsi
ón (convulsion) = kumbulsIY
Ón
I am not sure if there are actually spelling rules that we have to follow with regard to the conversion of the diphthongs to Pilipino, but it seems to me that in each group of examples above, these “rules” apply:
Group 1 – when the diphthong is on the first syllable or on the stressed syllable, the addition of “y” or the replacement of the first vowel with “y” depends on how the Spanish words are pronounced.
Group 2 – when the diphthong is on the last syllable and a) a single consonant precedes the diphthong, “y” replaces the first vowel; and
Group 3 – b) when 2 adjacent consonants precede the diphthong, “y” is added between the vowels.
There might be exceptions to these, but these “rules” may come in handy in helping you decide. That’s assuming, of course, that you are familiar with the spelling of some Spanish words.
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