Grammar problem from a dictionary

Hello! I found this explanation of “prayer” in a Cambridge dictionary:

“A prayer is the words that someone says or thinks when they are praying”

I don’t understand why “they are” is used for “someone”. Isn’t “someone” singular, because it is followed by “says” and “thinks” ???

Please explain this to me!
Thanks!

.
Grammatically you are right, and if you are taking a language proficiency test, you should correct this to he or she is.

However, in spoken English, they/their/them have been the pronouns for singular persons of unknown gender for centuries, and they are more and more widely accepted in most situations these days.