1. Doze off : fall asleep, often during the day
Ex : I tried to wake Ram when I saw hin dozed off while writing.

2. nod off : fall asleep (without meaning to)
Ex : My Boss nodded off during the meeting.

3. Sleep in : sleep for a longer time than usual
Ex : During weeked I noramally sleep in late.

4. Sleep through : not wake up when your alarm rings
Ex : Akash sleep through his alarm again, I am sure he will be going to miss his bus.