The reason that.
The second sentence states the reason for the action or state expressed by the first sentence. The first sentence is introduced by manu ay, the second sentence by ya or ti.
Manu ay tumaba nan bābuy'u ya impaphod'un pinangapangan.
The reason that my pig is becoming fat is that I cared for it, feeding it continually.
Manu ay ma'ung'ūnga' ti un hay lūtay gun iyālin Dummūlaw.
The reason I am thin is because dirt is what Dummūlaw has been bringing (me).
See sec. 7.26.2.2.