Credulous (adjective)

Inclined to believe too readily; gullible.

Origin:

From latin credulus, from credere ("to believ.e")

Examples:

1. He was too credulous and believed everything he was told.
2. She was so credulous that she fell for the scam.
3. The salesman took advantage of his credulous nature.
4. He was a credulous person and always believed in others.
5. The story seemed too fantastical to be true, but she was a credulous person and believed it anyway.