Genuine (adjective)

1. Truly what something is said to be; authentic.
2. Not counterfeit or copied; original.
3. Sincere and authentic in feeling, behavior, or expression.
4. Representing one's true nature or character.

Origin:

Late middle english: from latin genuinus, from genus 'race, birth'.

Examples:

1. The painting was authenticated as a genuine Rembrandt.
2. She gave a genuine smile of greeting.
3. He showed a genuine interest in her work.
4. The product is guaranteed to be 100% genuine leather.
5. He had a genuine talent for playing the piano.