Can anyone kindly explain to me the difference between these two words?
Both words can be used both as nouns and as adjectives. The only overlapping senses would likely occur in their uses as nouns, which are less common than their adjectival uses.
As an adjective, percipient today mostly means perceptive. The OED gives this meaning:
That perceives or is capable of perceiving; conscious; perceptive, discerning.
That really doesn’t match with what prescient means. To find the purported synonymy, we must instead look to the noun senses. As a noun, percipient is restricted mainly to two specific domains, either philosophy or “parapsychology”:
- Chiefly Philosophy. A person who or thing which perceives.
- Parapsychology. A person who perceives something outside the range of the senses; a person with extrasensory perception.
It’s the second noun sense that aligns with people having prescience, worlds with seers and prophets, psychics and fortune tellers.
As for prescient, the OED provides two adjectival senses:
- Having foreknowledge or foresight; foreseeing.
- Of, relating to, or arising from prescience.
It is mainly in the speculative worlds of science fiction or fantasy that one encounters prescient used as noun to indicate a person with prescience, whether that’s Paul Atreides from Dune or Cassandra from the Iliad.* Those are where people who are called “prescients” would be like people called “psychics”.
Words with meanings similar to adjectival sense of prescient include foreseeing, far-sighted, long-sighted, prevoyant, precognitive.
Be aware that prescients the plural noun and prescience are pronounced identically, so it would be easy to mishear one for the other.
* BTW, Atreïdes also derives from the Iliad.