The phrase "a certain expression" is correct and usable in written English.
It can be used when referring to a specific expression that is not named or is known to the reader or listener.
Example: "In her speech, she used a certain expression that resonated with the audience."
Alternatives: "a particular phrase" or "a specific term".
Most of the genes were highly expressed at the early developmental stage (E-L31) and maintained a certain expression levels in the following process (Fig. 5b).
He wore a certain expression I recognized from China—slightly stunned, a little overwhelmed, completely out of his element.
One of your most fascinating findings is that if a person merely arranges his face into a certain expression, he will actually feel the corresponding emotion.
Viewed from a certain angle, wearing a certain expression, it's still possible, just, to see the flicker of the Rourke who once was, but it's only a flicker.
He wore a certain expression I recognized from China — slightly stunned, a little overwhelmed, completely out of his element.
A novel high-throughput screening method based on the Luminex® xMAP™ bead technology was developed allowing a rapid evaluation of a certain expression strategy.
All of them have been mocked by Internet commenters for having a certain unintentional expression when their faces are not in motion — a look best described as vaguely annoyed, maybe a little judgy, perhaps slightly bored.
A Confluo aggregate (see table below) evaluates a computable function on an attribute for all records that match a certain filter expression.
REGULAR Facebook perusers are no doubt familiar with a certain photographic expression: a pout-producing, cheekbone-enhancing pose featuring pooched-out lips and sucked-in cheeks.
Viewers will connect their own dots, but pale green, the fragmentation of the body, a certain melancholic expression and triangles forge some of the links between works by Ferdinand Hodler, Fredrick Kiesler, Henry Fuseli, Georg Baselitz, Pollock, Klee, Picasso and Otto Dix.
In contrast, for a dielectrically highly conducting interface the electric potential is continuous across the interface whereas the normal electric displacement has a discontinuity across the interface which is proportional to a certain differential expression of the electric potential.
