sino

1. Basic Usage
Sino is used at the beginning of a sentence to ask "Who?" It is usually followed by the marker ang to point to the specific person being asked about. In casual, everyday speech, native speakers overwhelmingly replace ang with 'yung (or iyong) when asking about a specific person (e.g., Sino 'yung kasama mo?). When sino is followed directly by a pronoun, such as Sino ka? (Who are you?) or Sino ito? (Who is this?), the marker ang is not needed because words like ka and ito are already Ang-form pronouns. They inherently carry the 'ang' case, so adding the word ang before them would be grammatically redundant.

2. The Linker '-ng' vs. Contraction
When sino is followed by a noun, it can take the -ng linker to become sinong (e.g., Sinong bata? - Which child?). However, it can also be followed by the contraction of sino ang, written as sino'ng. This creates a contrast in meaning: Sinong bata? means 'Which child?', while Sino'ng bata? means 'Who is the child?'. When followed by a verb, it is very commonly contracted to sino'ng in speech (e.g., Sino'ng kumain? - Who ate?), though Sino ang kumain? is perfectly grammatical and standard in formal writing. In casual texting, the apostrophe is often dropped, making context important.

3. Question Particles
In natural conversation, speakers often add the ba particle to clearly signal a question. Another highly common particle is kaya, which adds a sense of wondering or speculation.
Examples:
Sino ba ang kasama mo? (Who is with you?)
Sino kaya? (I wonder who?)

4. Other Case Forms
It is important to distinguish sino from its other case forms:

• Sino: Who / Whom (Subject/Topic)
• Kanino: Whose / To whom. When meaning 'whose', it often starts a phrase (e.g., Kaninong libro ito?). When meaning 'to whom', its placement is flexible and can appear at the end of a clause (e.g., Ibibigay mo ito kanino?). It is also used with prepositions, such as para kanino (for whom) and nasa kanino (with whom / in whose possession, e.g., Nasa kanino ang susi?).
• Nino: By whom / Whose. When meaning 'whose', it must follow the noun it possesses (e.g., Libro nino ito? - Whose book is this?). When meaning 'by whom', it acts as the actor of a patient-focus verb (e.g., Kinuha nino? - Taken by whom?).

5. Pluralization
To ask for a list of people, you use reduplication: Sino-sino. While you may see the traditional spelling sinu-sino, modern standards maintain the 'o' in the root. Native speakers often use the singular sino even for groups in casual speech. Other case forms also reduplicate for plural answers, such as kani-kanino (whose/to whom - plural) and nino-nino (by whom - plural). However, note that while nino-nino exists in traditional grammar tables, it is virtually non-existent in actual speech; native speakers rarely use it and prefer to rephrase the sentence.

6. Respectful Speech
In formal situations, include the po enclitic to remain polite. Additionally, politeness often involves pronoun substitution; using the third-person plural sila instead of 'ka' or 'kayo' shows deep respect.
Example: Sino po sila? (Who are you? [polite])