It is the source, or the headwaters.
The 'source' of a river.
Spring
mouth
Source.
it means good
A word meaning to leave out which begins with an "o" is omit.
"Ik" is an Afrikaans word that begins with the letter "i." It means "I" in English.
Reversal is a synonym for the word switch. It begins with the letter r.
New Mexico is west of the Mississippi River.
Alternative
ample
angling