What is the difference between sinew and tendon?

I wonder what the difference between sinew and tendon is. I searched for it but didn't get any clear answer:

https://www.quora.com/Whats-the-difference-between-sinew-and-tendon:

They are often used interchangably but to be technical, a tendon connects a muscle to a bone. The term sinew also seems to include ligaments which connect bones to bones. It is however, not a medical term.

https://answers.yahoo.com/question/index?qid=20070410182936AA2Kcnk

Sinew is another word for muscle which is the functional unit of movement.

Tendons connect bone to muscle to make movement possible: The muscle contracts and pulls the bone that it's connected to Source(s)

http://the-difference-between.com/tendon/sinew :

Sinew is a synonym of tendon. As nouns the difference between sinew and tendon is that sinew is (anatomy) a cord or tendon of the body while tendon is (anatomy) a tough band of inelastic fibrous tissue that connects a muscle with its bony attachment.

http://www.thefreedictionary.com/sinew

sinew = tendon

https://en.wikipedia.org/wiki/Tendon

A tendon (or sinew) is a [...]

Is sinew a synonym for tendon, and if not what is the difference?