The noun pinnacle is used to talk about the highest or culminating point of something, most commonly the time in one’s career when they are most successful or a specific achievement that caps one's career. In architecture, a pinnacle is a small, upright structure rising above the roof of a building or capping a tower. In nature, a pinnacle is a lofty peak of a mountain or a pointed, towering part of a rock formation. The theme of capping, crowning, or being positioned atop something is what threads these senses together. The more general word peak is the appropriate choice for talking about maximum prices (oil prices reached their peak) or maximum volume (traffic was at its peak).

To illuminate is to supply with light or to light up. But this verb is not used in exactly the same way as the much more general verb light. For instance, light is more appropriate to talk about the action of igniting or setting something to burn, as a candle. But illuminate is more appropriate for talking about what that lit candle will do: illuminate the room! Stars illuminate the night sky, just as festive lights illuminate residential streets during the holidays. To illuminate a path forward is to shed light on the best course of action—unless of course the path is a literal one from, say, the mailbox to the front door after sunset. In which case, a flashlight should do the trick! Illuminate can also refer to shedding light on a subject, as if to make it more clear or comprehensible.

To fret over something is to feel or express worry, annoyance, or annoyance about it. The earliest senses of this term in English had to do with devouring or consuming in the literal sense—as in moths fretting your favorite sweater (heaven forbid!). The verb has of course evolved since then, with the theme of consuming taking a turn: rather than expressing the act of consuming, fret now conveys being consumed or eaten by something. Interestingly, the critters who would do the fretting were usually small (like moths), which perhaps explains why the current sense of fret suggests incremental or gradual gnawing away at one’s peace of mind.