never
At no time; not ever, not even once.
Never means not at any time, not ever, not once. When you say you've never been to Alaska, you mean you haven't gone there in the past and you're not there now. When your teacher says she's never seen such creative artwork, she means not once in her entire teaching career has she encountered anything quite like yours.
The word carries a sense of absoluteness. If you say you'll never give up on learning to skateboard, you're making a strong statement about your determination. If someone says they've never tasted chocolate, that's remarkable because chocolate is everywhere.
People often use never for emphasis or exaggeration. When your brother complains, “You never let me have a turn,” he probably means “not often enough” rather than literally zero times ever. This exaggerated use makes conversations more dramatic, but it can also start arguments, since the other person might point out the times you actually did let him have a turn.
The opposite of never is always. Between these two extremes lie words like sometimes, often, and rarely. Understanding this spectrum helps you speak more precisely. Instead of saying “It never rains here,” you might more accurately say “It rarely rains here.”