This is the 42nd most frequent Arabic word.
الذين
"الذين" means "those who" or "the ones who" in English, used for masculine plural.
"الذين" is used to introduce a relative clause specifying the subset of "الطلاب" (the students) who have the quality of studying diligently.
الطلاب الذين يذاكرون بجد يحققون النجاح.
The students who study diligently achieve success.
"الذين" is employed to link "الأشخاص" (people) with the quality of helping others.
الأشخاص الذين يساعدون الآخرين يساهمون في صنع المجتمع أفضل.
People who help others contribute to making society better.
"الذين" refers to "المعلمون" (teachers) and connects it to the clause describing them as respecting their students.