Difficult to overcome, solve, or decide.
Contributing (especially if subtly) to discrimination (such as racism, sexism, homophobia, transphobia, or ageism).
Not settled, uncertain, of uncertain outcome; debatable, questionable, open to doubt.
a problematic analysis
A problem or difficulty in a particular field of study.
Certain to act or be a specified way.
Physically secure and certain, non-failing, reliable.
Certain in one's knowledge or belief.
Without doubt, certainly.
Yes, expressing noncommittal agreement or consent.
Yes; of course.
You're welcome; polite response to being thanked.