The 19-year-old made the comment on the social network on 29 November accompanied by a picture of the Spain defender getting his teeth whitened.
The Tweet read: “What f*** is he doing? This guy is gay… he does everything except play football.”
Suso, who has made 13 appearances for the Reds, has been warned about his future conduct.
The FA said in a statement: “Following an independent regulatory commission hearing yesterday, Liverpool’s Jesus Fernandez Saez (Suso) has been fined £10,000 and warned as to his future conduct for a comment posted on Twitter.
“The charge, which the player admitted and requested a paper hearing, was that he acted in a way which was improper and/or brought the game into disrepute in that the comment was posted on his Twitter account and included a reference to a person/s sexual orientation and/or disability.”
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