pag--an, pagsi--un, pag--un, pa--un
To do s.t. all together, simultaneously, or in unison.
When pag--an is used the focus is on many people working together on one object. When pag--un/pagsi--un is used the focus is on the object being uniformly changed like the length of one's hair, length of pieces of bamboo, length of a group's marching steps, etc.
If we don't all work together, it will be a long time before we finish our work.
Pagsisama-samahun bi pengka' bi.
March in unison.
Get your steps to be in unison with theirs.