"The humidity is high today."
Translation:اَلْرُّطوبة عالْية الْيَوْم.
-tun in fact. 3áliyatun
This word is an adjective, but predicative (i.e. telling the status of the humidity, الرطوبة). For this reason, it did not mimic the noun (الرطوبة) in definition (with AL), and hence, it comes without (AL), and accordingly, must has tanwin (or Nunation), which is (-un) sound at its end.