kruta

One root, no seam. Krut- plus the adjectival -a, and that is the whole word. It is worth flagging precisely because it does not decompose: at this point in the course you have met enough compounds that the reflex is to reach for a knife, and there are perfectly good roots that simply have to be learned. Kr- is nothing, -ut- is nothing, and there is no Esperanto affix hiding in either.

It also comes from the other half of the vocabulary. Most of the words in this chapter are Latin or French with the ending swapped. Kruta is Slavic, and Esperanto has a real Slavic layer that learners under-notice: krado, klopodi, barakti, svati, celo, pravi, nepre, ĉu. Zamenhof's first language environment was Russian, Polish and Yiddish, and where a Romance word would have been long or ambiguous he took a short Slavic one instead. When a root looks unlike anything you expect, this is usually why.

Range. Kruta covers a slope, a stair, a cliff, a bank, a path - anything with a sharp gradient. It also does the figurative work English gives to a steep rise: kruta plialtiĝo de la prezoj is a sharp increase in prices. The opposite is malkruta, gentle, or more idiomatically milda of a slope; the noun is krutaĵo, a steep place, using the -aĵ- suffix for a concrete thing with that quality. A deklivo is the slope itself, so kruta deklivo is the pairing you will meet most.