i- + -in- + Reduplicated Root

In Filipino, verbs are categorized by aspect rather than tense. The progressive aspect represents actions that have started but are not yet finished. Along with -in and -an verbs, i- verbs fall under the broader overarching category of Object Focus (or Patient Focus) verbs.

1. Formation Rules:

• Consonant-initial roots: i- + (reduplicated first syllable of root with -in- infix) + root. Example: sulat (write) becomes isinusulat (is being written) (the first syllable su is reduplicated with the infix -in- to become sinu).
• Vowel-initial roots: ini- + (reduplicated first vowel) + root. Example: abot (hand over) becomes iniaabot (is being handed over). Note that i- verbs do not use a hyphen when adding i- or ini- to a vowel-initial root (e.g., iniaabot, not ini-aabot). Note: For roots starting with 'i', the resulting three consecutive i's are simplified to two in standard orthography (e.g., ikot -> iniikot, meaning 'is being turned'). However, you will frequently encounter the unsimplified version (iniiikot) in casual writing and social media.
• L, R, W, Y, and H-initial roots: Roots starting with L, R, W, and Y commonly use the ni- allomorph to avoid awkward sounds, although the -in- infix form is still used in some dialects and older literature. Formula: i- + ni- + (reduplicated first syllable) + root. Example: lagay (put) becomes inilalagay (is being put) (i- + ni- + la + lagay). Meanwhile, H-initial roots can use either this ni- form (inihahagis, meaning 'is being thrown') or the standard -in- infix (ihinahagis, meaning 'is being thrown').

2. Usage and Focus:
The i- prefix is versatile. In theme focus, it highlights the object being moved or conveyed, which is marked with ang. However, in benefactive focus, the i- (often as ipag-) highlights the person for whom the action is done; in this case, the beneficiary is marked with ang. Additionally, it is the base prefix for instrument focus (usually taking the form ipang- or ipinang-), which highlights the tool used to perform the action. The actor is always marked with the nonfocused ng-case (which includes the marker ng for common nouns, ni/nina for personal names, and ng-pronouns) in these object-focus constructions. If the focused object, beneficiary, or instrument is a pronoun, it must use the ang-set (nominative) pronouns (like ako, ka, siya), contrasting with the ng-set actor pronouns. Crucially, following the rule for second-position words, enclitic actor pronouns (like ko, mo, niya) must directly follow the verb, coming before the focused object (e.g., Isinusulat ko ang liham, meaning 'I am writing the letter', not Isinusulat ang liham ko).

3. Register Differences:
In formal writing and news, the full form (e.g., ibinoboto, meaning 'is being voted for') is standard. However, in conversational Filipino, speakers often drop the initial i- (e.g., binoboto). Note that dropping the i- makes these verbs look exactly like standard -in object focus verbs (like kinakain, meaning 'is being eaten'), which can be a major source of confusion when trying to reverse-engineer the root word. While common, learners should use the full form in academic or formal contexts to become proficient in the language.