Filipino Question Words in Plural Forms

Filipino question words are also subject to plurality rule. The plural forms of question words are used when the expected answer or subject being referred to is more than one or in plural form as well.

There are two basic rules to remember in forming the plural forms of the question words. The first rule is to duplicate the whole question word if the question word that is used is composed of two syllables only (anó, sino, alín, saán, ilán).
The second rule in pluralizing question words is to duplicate the first two syllables of the question word if the question word is used is composed of three or more syllables (kanino, magkano, kailán). Kaí-kailan is rarely used and took on a distinct meaning on its own. These days, kaí-kailan would mean "recently" as in, "I just arrived recently."Sínu-sino and anú-anó used to be the plural forms of sino and anó respectively. Changing the letter O in the first word into letter U is an outdated rule for these question words. However, people still say and may prefer using this rule. The diffence between sínu-sino and síno-sino is barely noticeable in an actual conversation. In a grammatical sense, however, these are considered erroneous and out-of-date.

Násaan and Bakit do not have plural forms for the simple fact that nothing can be in the same place at the same time nor can there be a more than one explanation for a particular thing or event.