siya / niya / kaniya

In Filipino, pronouns change based on their role in the sentence. Both siya and niya act as second-position words when they are arguments of the verb, meaning they generally follow the first word of the clause.

Important Note on Usage and Pronunciation: While siya and niya are primarily used for animate nouns (people and animals), they are typically dropped or replaced by demonstratives for inanimate objects (like ito, iyan, or iyon for 'it', and nito, niyan, or niyon for 'its'). Using siya or niya for inanimate objects (e.g., Ano ang kulay niya?) is an informal colloquial trend, not the standard rule. In spoken Filipino, siya is almost universally pronounced (and often informally spelled) as sya or sha, and niya as nya.

• Siya (Ang-form): Used for 'he' or 'she' when the person is the focus. While it usually follows the first word (like Hindi siya gutom), it can also start a sentence if it is the predicate (e.g., Siya ang guro). Note that if a monosyllabic pronoun (like ko or mo) or an enclitic particle (whether monosyllabic like ba, na, pa, or bisyllabic like naman, sana, pala, yata) is present, the bisyllabic siya will move after it (e.g., Nakita mo siya, Wala na siya, or Wala naman siya).
• Niya (Ng-form): Used for 'his' or 'her'. When showing possession, it follows the noun or the first word of the noun phrase (e.g., Bahay niya ito). Note that when niya (or siya) interrupts a linked phrase (like an adjective and a noun), it 'steals' the -ng linker from the preceding word. For example, in Ang bago niyang bahay (His/her new house), the adjective bago modifies bahay (underlyingly: Ang bagong bahay niya), but the enclitic niya interrupts the phrase and takes the linker. When acting as the actor in an object-focus sentence, it follows the enclitic rule and moves to the second position (e.g., Kinain niya ang tinapay). If a monosyllabic pronoun (like ka) or an enclitic particle (whether monosyllabic like ba, na, lang, or bisyllabic like naman, sana) is present, the bisyllabic niya will prescriptively follow it (e.g., Nakita ka niya, Kinain na niya, or Kinain naman niya). However, in colloquial spoken Filipino, because niya is often pronounced as a single syllable (nya), it frequently precedes bisyllabic particles (e.g., Kinain niya naman). Furthermore, when both bisyllabic pronouns niya and siya are in the same sentence, the Ng-form always precedes the Ang-form (e.g., Nakita niya siya). Because Filipino pronouns are gender-neutral, this combination creates high ambiguity (it can mean 'He saw her', 'She saw him', 'He saw him', or 'She saw her'). To avoid confusion, Filipinos often replace one of the pronouns with a name or noun.
• Kaniya (Sa-form): Used as an independent possessive ('his' or 'hers'). To indicate direction or location ('to him/her'), it must be combined with the preposition sa (i.e., sa kaniya). To mean 'for him/her', it is combined with para sa (i.e., para sa kaniya). It is not an enclitic and can appear in various positions. It is often contracted to kanya, which is a widely accepted colloquial spelling in everyday writing, though kaniya remains the formal standard. It can also be placed before a noun using the -ng linker to show possession (e.g., kaniyang bahay or kanyang bahay).
  Examples: Ibigay mo sa kaniya. (Give it to him/her.) / Ito ang kaniyang libro. (This is his/her book.)