か否か

か否か is a formal, written way to say 'whether or not' something is the case. It asks you to consider two possibilities: that X is true, and that X is not true. It is commonly used in analytical writing, reports, debates, and formal conversation where the speaker wants to present both sides or conclude after weighing evidence. It tends to appear in contexts where nuance and nuance of certainty are being discussed, rather than in casual speech. When forming sentences, attach か否か to the clause that expresses the condition or statement you're evaluating. The phrase can be used with nouns, verbs in plain form, and with adjectives (い-adjectives and na-adjectives) by treating the clause as a simple proposition: for na-adjectives you typically use the form with だ/ではない before か否か.