The phrase "a natural expression" is correct and usable in written English.
It can be used to describe a phrase or manner of speaking that feels instinctive or typical in a given context.
Example: "Her laughter was a natural expression of joy that filled the room."
Alternatives: "an instinctive response" or "a genuine reaction".
"It's a natural expression of human nature," he said.
It's a natural expression of its creative vision.
His arms are a natural expression of his zeal.
If Mr. Clinton's progressive internationalism took a while to crystallize fully, it was nonetheless a natural expression of his identity.
To offer sacrifice on an altar seemed a natural expression of gratitude to any dead, or even living, benefactor.
Forgiveness, like other positive emotions such as hope, compassion, and appreciation, is a natural expression of our humanity.
Characterization of the integron further revealed presence of promoter sequence (Pc) upstream of the gene cassette highlighting its significance as an active natural expression vector.
And yet there was a whiff of destiny about his 18-16 triumph over Matthew Stevens, a player whose natural expression is that of a man who fears he may have mislaid his winning lottery ticket and who certainly lost his way here after starting the day with a four-frame overnight lead.
There are head-fakes toward an interesting conversation on aesthetics: what happens when an artist's natural expression is the same as someone who is already established?
It is unclear whether this observation is a melanoma-driven effect (active suppression of NKp30 expression), or whether individuals with a natural lower expression of NKp30 are more susceptible to the development of melanoma (a selection effect).
Don't stare at her, try to display a natural, interested expression, rather than an intensive concentrated expression that you would normally use during a deep, meaningful conversation.
