The infix -um- and its derivatives

Another noticeable difference is the infix -um- which has also undergone a process of simplification since the

Spanish era.

The infix -ungm- which has disappeared from virtually all contemporary Tagalog dialects. In modern Tagalog, -um-

serves as the infinitive, imperative, and completed (past) forms. So what distinguishes the phrase kumain

ka (either "eat" or "you ate") is context and tone). This infix is cognate with similar infixes in other Philippine

languages. They, too, also make a distinction between the infinitive the past forms:

Apparently the infinitive form comes from Proto-Philippine *-um- and the past one from Proto-Philippine *-umin-.

Furthermore, there were variants of -um- that had to do with phonetic environment. For example, if the first

vowel of a rootword was /i/, then -um- would optionally change to -im-. This is called vowel harmony. For

comparison's sake, I'll use the rootword tingin as an example: