ang / ng / sa

The ang / ng / sa system is the backbone of Filipino grammar. Most common noun phrases are preceded by one of these markers, though they are omitted in specific cases like existential may constructions. Note that while the marker ng is spelled with two letters, it is always pronounced as 'nang'. Do not confuse it with the separate word nang, which is used for adverbs and conjunctions. It is also distinct from the -ng linker used to connect adjectives to nouns.

• ang (Focus Marker): This identifies the 'Focus' or the most important participant in the sentence. It usually makes the noun specific (often translated as 'the'), but it is also the standard marker for generic nouns or class representations (e.g., Ang aso ay hayop). In Filipino, the speaker's choice of which participant to focus on dictates which affix the verb must take.
• ng (Genitive Marker): This marks nouns that are not the focus. When marking the object of an actor-focus verb, it indicates an indefinite common noun (which can translate to 'a/an', 'some', or no article for plural and mass nouns). If you want to refer to a definite object (like 'my book'), native speakers overwhelmingly prefer to use an object-focus verb instead (e.g., Binasa niya ang aklat ko). Note that proper names are inherently definite. While they technically take the oblique marker kay when acting as the object of an actor-focus verb, native speakers usually avoid this construction entirely, strongly preferring to use an object-focus verb instead (e.g., Nakita ko si Juan, not Nakakita ako kay Juan). The marker ni is strictly for possessors and actors, never objects. The ng marker frequently translates to 'the' when marking a possessor or the actor of an object-focus verb. It is also used as an instrumental marker to show what was used to perform an action (e.g., hiniwa ng kutsilyo, sliced with a knife).
• sa (Oblique Marker): This is a versatile marker for locations, directions, and time (in, on, at, to, from). For time expressions, it is often used for future or habitual actions, like sa Lunes (on Monday), while past periods typically require the marker noong (e.g., noong Lunes). Note that noong strictly replaces sa for time expressions in the past, whereas sa is still retained for locations and directions regardless of tense (e.g., Pumunta ako sa Maynila noong Lunes). However, sa is still used in past contexts for exact dates, times, or years (e.g., Ipinanganak ako sa ika-5 ng Mayo). Crucially, if an actor-focus verb is used with a definite common noun object, the marker sa is used instead of ng. This creates a clear definiteness contrast: for example, Tumingin ako ng aso means 'I looked at a dog' (indefinite), whereas Tumingin ako sa aso means 'I looked at the dog' (definite). Many common directional actor-focus verbs (like punta, tingin, bigay) frequently use sa for their definite object or destination. Note that 'for' typically requires para sa rather than sa alone.

To make these plural, simply add mga (pronounced as 'manga') after the marker (e.g., ang mga). When talking about people's names, this system shifts to the si / ni / kay system. For example, si replaces ang for focused personal names, and using ang with a person's name (e.g., ang Juan) is ungrammatical. This system has its own plural forms: sina, nina, and kina. This three-way system is so fundamental that personal pronouns and demonstratives (like ito, nito, and dito) strictly follow it as well. Understanding how these markers interact with verb focus is the most important step in becoming proficient in Filipino.