Oka
The answer is the Aar (another accepted spelling for the Aare.)
Saône
The famous Han Dynasty (202 BC - 220 AD) shares its name with the Han river, a tributary of the Yangtze river.
The root word of 'tributary' is "tribute," which comes from the Latin word "tributum" meaning "a tax or payment."
One seven letter word, One two letter word and a five letter word, One three letter word and a four letter word, One three letter word and two two letter words, Two three letter words, Three two letter words, A two letter word and a four letter word, A six letter word, A two letter word and a three letter word, A five letter word, Two two letter words, A four letter word, A three letter word, or A two letter word.
The Ohio River is a tributary of the Mississippi River. In the ancient world, Egypt became a tributary of the Roman Empire.
I've is a three letter word. I'll is another three letter word.
A three letter word for a summit = Top.
Imp is a three-letter word for rapscallion.
A three letter word for help is aid.
A three letter word for gender is sex.
A three letter word for debt is owe.