The objective can be:
a) Concrete (a specific thing: table, chair, apple, house, etc).
b) Abstract (quality considered separately that is part of the concrete: length, mass, time, volume, etc.).
The subjective can be:
a) Abstract (love, hate, happiness, peace, etc).
b) Imaginary (it is unreal: dragon, mermaid, unicorn, etc).
Time is the property we abstract from the phenomena of occurring continually. From a clock we abstract a measure, the quantity of duration. Similarly, from a body we abstract its mass or its length.
Elvis Sibilia, Florida, USA