objektiva

Where it does cut, and where it does not. Objekto is a live Esperanto root at rank 688, so objektiva genuinely does contain a word you already have. The -iv- on the end, however, is not one of the official affixes: Esperanto's list is closed, and -iv- is not on it. It is a real thing all the same, and the Reta Vortaro carries it as an unofficial suffix for active capability, set against the Fundamental -ebl- for passive capability: kreiva, produktiva, informiva. The full picture, including why aktiva and naiva and kultivi are single roots you must not cut at that seam even though they end the same way, is in the unofficial affixes. Treat objektiva as a borrowed international word that happens to sit on a root you know, and do not go coining new ones with -iv-.

The pair, and only one half has a page. Objektiva is what belongs to the object; subjektiva is what belongs to the subject, the person doing the looking. Esperanto has both, built on objekto and subjekto exactly as you would expect, and subjektiva has not yet earned a page in this course. The nouns are objektiveco and subjektiveco, and the adverb objektive is the form you will meet most often in argument: objektive parolante, objectively speaking.

Nearby, but not the same. Justa is fair, which is about how you treat people. Neŭtrala is uncommitted, which is about which side you are on. Objektiva is about whether your account matches the thing itself, and you can be objective and partisan at once, which is the whole reason the word is worth having separately.