You can describe something as abstruse if you find it highly complicated and difficult to understand.
Abstinence is the practice of keeping away from or avoiding something you enjoy—such as the physical pleasures of excessive food and drink—usually for health or religious reasons.
When you abscond, you leave suddenly from a place that has imprisoned or persecuted you, or you leave from a place with something that doesn't belong to you.
Someone who is abstemious avoids doing too much of something enjoyable, such as eating or drinking; rather, they consume in a moderate fashion.
When an idea is abstract, it is not based on a sensed material object but is rather based on a mental concept or is purely theoretical.
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