* "The artist's abstract paintings were full of vibrant colors and swirling shapes." (Describing the style of the paintings)
* "He presented an abstract concept that was difficult to grasp." (Describing the nature of the concept)
* "The lawyer presented an abstract legal argument." (Describing the level of theory in the argument)
* "She loved reading abstract poetry." (Describing the type of poetry)
* "The students struggled to understand the abstract mathematical equations." (Describing the difficulty of the concepts)
As you can see, "abstract" as an adjective describes something that is not concrete or specific, but rather conceptual or theoretical.