Straight lines next to curvy lines add variety. Organic shapes among geometric shapes add variety. Bright colors next to dull colors add variety. Note: If an artist uses variety to draw the viewers attention to a specific area in a composition then variety morphs into emphasis, also a principle of art.
Unity refers to how different elements of an artwork or design work come together and create a sense of wholeness. It can be achieved through proximity, simplicity, repetition and continuation.
