si

The marker si is a Focused Personal Marker. Its primary job is to introduce a proper name (or a title used as a name) that serves as the 'focus' or subject of the clause, as well as the predicate in equational sentences.

Key characteristics include:

• Personal Names and Titles: Use it for people (si Maria) and pets (si Fido). When using titles like Nanay (Mom) or Titser (Teacher), using si implies a personal, familiar relationship. It is also used to personify animals, objects, or concepts in folklore and literature (e.g., Si Pagong at si Matsing - The Turtle and the Monkey). In contrast, using ang makes the reference more formal or role-based.
• Equational Sentences: si is essential when a name functions as the predicate, such as when introducing yourself or someone else (e.g., Ako si Juan - I am Juan).
• Not for Places: In formal, standard Filipino, si is generally not used for geographical places, countries, or brand names. You typically use ang for these (e.g., ang Maynila, ang Pilipinas).
• No Pronouns: Never use si with personal pronouns like ako (I) or siya (he/she). Pronouns already have their own focused forms (e.g., ako, siya), so adding si is incorrect.
• Singular Focus: It is used for one person. If you are talking about multiple people, you must use sina. Sina is used both for lists of specific names (e.g., sina Maria at Juan - Maria and Juan) and to mean 'and company' when followed by a single name (e.g., sina Maria - Maria and her group). Note that while you will often hear native speakers say sila Maria in casual speech, sila is strictly the pronoun 'they'. Using it as a marker before a name is grammatically incorrect in standard Filipino; always use sina instead.
• Grammatical Function: It has no direct English equivalent whatsoever. It does not mean 'is,' 'the,' or 'a.' It is purely a grammatical tag that indicates the role of the name in the sentence. It is the required marker when answering sino (who) questions specifically with a proper name.
• Doer vs. Receiver: Because of Filipino's Focus And Participant Roles, the focused subject marked by si is not always the doer of the action. It can be the receiver if an object-focus verb is used (e.g., Tinawagan si Maria - Maria was called).
• Contrast with Other Markers: si is strictly for the focused subject. For possession or non-focused actors, use ni (e.g., aso ni Maria) or its plural nina. For direction or location, use kay (e.g., ibigay kay Maria) or its plural kina.
• Placement: In the standard Predicate-First sentence structure, it appears after the predicate. This means si + [Name] typically comes after the verb or adjective (e.g., Matalino si Maria - Maria is smart / Tumakbo si Juan - Juan ran). This is highly counter-intuitive for English speakers who default to Subject-Verb order. In the Ay Inversion structure, it appears before the ay marker.
• Enclitic Placement: Second-Position Words (enclitic particles like ba, po, na, or pa) cannot be placed directly after si. They must follow the predicate or the name itself. For example, say Mabait ba si Maria? (Is Maria good?) instead of Mabait si ba Maria?
• Colloquial Personification: While standard Filipino uses ang for brands, in casual speech, si is often used to personify companies, brands, or apps (e.g., Sira na naman si PLDT - PLDT is broken again).