The phrase "as though certain" is correct and usable in written English.
It can be used to express a hypothetical situation or to indicate that something appears to be true, even if it is not confirmed.
Example: "She spoke about the project as though certain it would succeed, despite the challenges ahead."
Alternatives: "as if sure" or "as if confident".
It was as though certain words had become detached from the objects they signified.
Mrs. Acton liked to veil the weak electric lights with beaded glass fabric, dappling the stucco walls in shadowy patterns, as though certain rooms were seen through gauze.
I'd rather see my books described as "issue books" than see other books labelled "boy books" or "girl books" ― as though certain readers are only supposed to stick to certain books because of their gender.
The majority of the patients with the 14 bp deletion were women (13/17), and it seemed as though certain potential risk factors for carcinoma of the head and neck were less common in this group.
The rest are read as carefully as time permits, though certain titles will stand out in advance given the enormous attention they may have already received in certain venues.
It's not as though, up to a certain point, you have an OK amount of cancer, and then one day the doctor's like, "Uh oh! Too much cancer!" and then all your loved ones rush to your bedside (in your clean, cozy bedroom at home, of course – no catheter bags or grumpy nurses or antiseptic smells in this fantasy) for some poetic, wise goodbyes.
Two things, though, are as certain as can be.
As a result though, certain myths, some of which carry extra weight because they do in fact involve a kernel of truth, tend to circulate among academics about industry.
It looks as though a certain cat is out of a certain bag.
It sounded as though only certain choice passages, such as the end of Act IV, had been thoroughly rehearsed.
When Krzysztof Kieslowski died on March 13 , 1996 it was as though a certain kind of cinema had come to an end along with him.
