Answer: There are many interpretations of shade conditions and different people will use the terms differently. However, most plants do have a lighting preference and/or a soil moisture preference and the combination will affect how they grow.
Full sun would be full sun all day long, or full sun for at least six hours with those hours including noon. Sun all afternoon is usually considered hot sun and would better suit plants that prefer full sun than those that prefer part shade. Plants that prefer part shade will usually tolerate the cooler morning sun, especially if they have ample moisture. Plants that prefer shade to part shade will not tolerate afternoon sun, but may tolerate partial morning sun, meaning early in the day when it is still cool.
High dappled shade all day (from trees) can be considered a partial shade location. Dense shade from a building such as on the north side of a house or deep under a deck can be considered full shade. There are degrees of shade and to some extent there is always some trial and error in determining what will grow best in each shady location, because there is so much variation.
Sun for the afternoon is a hotter location than a sun all morning location. For this reason, it is better to select a sunlover for an afternoon sun spot. Also, a plant with a preference for partial shade to sun will be more likely to tolerate a location with full morning sun than it would afternoon sun.
When a partial shade to sun plant is grown at the maximum light level it will tolerate, it may need extra moisture to grow well. Conversely, a plant that prefers sun but tolerates partial shade may be able to grow with slightly drier soil in the shadier location.
I hope this helps you think about sun and shade conditions. Unfortunately there are no hard and fast specific definitions to give you, just an understanding of how to make some educated guesses. If you can observe plants in your neighborhood and see where they are located, this will help you judge your own growing conditions. This is one of the best indicators you can use. Remember too that you can always transplant if a plant seems to object to its lighting.
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