In the "abstract sense"—referring to ideas, qualities, or concepts rather than physical objects—the antonyms of
abstract describe things that are grounded, specific, or verifiable.
The primary antonyms include:

Concrete: The most direct opposite; refers to things that are perceptible by the senses or exist in physical form.
Tangible: Describes something real and able to be touched, or clearly definite.
Specific: Used when moving from general theories to precise, individual instances.
Actual / Real: Refers to things that exist in fact and reality rather than just in the mind.
Factual: Indicates something based on evidence and truth rather than theoretical speculation.
Material: Pertains to physical substance or matter.
Practical: Suggests something that is actionable or useful in a real-world setting.
Objective: Relates to objects or events that are external to the mind and can be observed.

Contextual Antonyms:

Representational / Figurative: In the context of art or denoscription, these are opposites of "abstract" as they depict the world as it appears.
Detailed / Precise: Used when the "abstract" in question is a summary or high-level overview.

Would you like to see examples of how to rephrase an abstract sentence into a concrete one?