That which expresses (a particular material)(noun)
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Use "expresser" in a sentence
"But it would say little to how a particular expression of (1)/(2) reflects of the expresser."
"Thomas is such a clear thinker and Mankiw clear expresser."
"It can be something very general — a good ear for realistic dialogue, for instance, or a gift for helping the reader care about the protagonist — or something very specific, like being a magnificent describer of the interiors of automobiles or a world-class expresser of silent disgruntlement."