en_tn_lite_do_not_use/mat/12/39.md

An evil and adulterous generation seeks for a sign ... given to it

Jesus is speaking about the people he is talking to. Alternate translation: "You are an evil and adulterous generation who demands signs from me ... given to you"

adulterous generation

Here "adulterous" describes people who are not faithful to God. Alternate translation: "unfaithful generation" or "godless generation"

no sign will be given to it except the sign of Jonah

"The only sign that will be given to it is the sign of Jonah" or "The only sign that God will give is the sign of Jonah"

the sign of Jonah

"what happened to Jonah" or "the miracle that God did for Jonah"