General:
* Feature: A distinctive characteristic or part of something.
* Facet: A particular part or element of something.
* Side: A particular point of view or perspective.
* Angle: A way of looking at or considering something.
* Perspective: A way of thinking about or understanding something.
* Viewpoint: A position from which something is seen or considered.
* Dimension: A measurable extent of something.
* Component: A part or element of a larger whole.
More specific:
* Appearance: The way something looks to the eye.
* Character: The nature or qualities of something.
* Nature: The fundamental qualities or characteristics of something.
* Phase: A particular stage or period of development.
* Form: The shape or structure of something.
For a more precise synonym, it would be helpful to know the context in which you want to use the word "aspect."