when
verb
°.
°.
"Do you know when they arrived?"
conjunction
°At what time.
"They were told when to sleep."
°At such time as.
"I’m happiest when I’m working."
noun
°(interrogative) What time; which time.
"Since when do I need your permission?"
°The time.
"A good article will cover the who, the what, the when, the where, the why and the how."