What is the correct word for someone who is mentally slow?!

Since words change all of the time, I wanted to find out what is the most current and correct way to say that someone is “slow” or “mentally slow” or “mentally challenged” or “simple minded”? I know of someone who is 100% functional in every way . . . however their brain just does not react quickly like people who are not mentally slow. I am trying to help this person get a job that will require very basic and simple skills, yet I do not know how to address potential employers to tell them about this person . . . because telling them that an employee candidate is “slow” or “mentally slow” or “mentally challenged” or “simple minded” just does not sound right, and seems that it could be conceived as degrading.

Are there better words I could use to convey this?

NOTE: Before you reply with an answer, let’s have some sensitivity and seriousness with my question. Please, no insensitive remarks or answers to my question. Thank you.

Max