This is the 1187th most frequent Arabic word.
شك
"Doubt" or "uncertainty."
Here, 'شك' refers to uncertainty or lack of surety about something.
لدي شك في الإجابة الصحيحة.
I have doubt about the correct answer.
In this case, 'شك' designates a questioning attitude or reconsideration of the findings.
شك العالم في اكتشافاته دفعه لإعادة التجربة.
The scientist's doubt in his discoveries drove him to reperform the experiment.
Here, 'شك' is used in an idiomatic expression to convey assuredness or certainty.