stratum
noun
a layer of material, naturally or artificially formed, often one of a number of parallel layers one upon another.
The grammatical form denoting more than one person, place, thing, or idea.
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
Those "layers" became second nature to Sis, whose books and other artwork now are noted for their stratums of design and meaning.
From Seattle Times ● Apr. 27, 2012