Whats the difference between sadness and depression.

''sadness is a normal reaction to a loss, disappointment, problems, or other difficult situations. Feeling sad from time to time is just another part of being human. In these cases, feelings of sadness go away quickly and you can go about your daily life. ''

''Depression is a mental illness that affects your mood, the way you understand yourself, and the way you understand and relate to things around you. People who experience depression may feel worthless or hopeless. Depression lasts longer than two weeks, doesn’t usually go away on its own, and impacts your life. It’s a real illness, and it is very treatable.''

i don't know im sorry.

it means your tired?