Negative adverb used before verbs, adjectives, and other adverbs to indicate negation; also used as a bound-form prefix to form terms with opposite meanings

to be afraid; to dread; to be scared of something

one; the number 1; single; alone

the number 10,000

Used to express a logical consequence or the next step in a sequence, meaning "then" or "in that case".

to worry; to be anxious that something might happen

Used to express a low-probability event or hypothesis, usually for something undesirable; in the unlikely event that; if by any chance.