Answer: You are asking a really good question and one for which there are no truly precise answers. Full sun (eg south side of your house) usually means direct sun all day long, or for at least six hours including the hour of noon. Keep in mind that hot afternoon sun on the west side will be more intense than all morning sun on the east side. Partial shade usually means several hours of direct morning sun or very late in the day, or bright dappled light such as through tall trees all day. Deep shade would mean no direct light, the shade could due to a building (center of the north side) or overhang or thick evergreen trees for example.
Keep in mind also that the amount of direct sun hitting the ground will change as the sun angle becomes higher in the summer, it is lower in the winter so some areas seem shady in January but are sunny in July.
Exposure can refer to the light, but it can also refer to the amount of wind the site receives, especially in the winter since a windy site is usually colder than a sheltered and protected one. I hope this helps.
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