evoluigi

One suffix, and the whole word falls open. Evolui is intransitive: a species, a situation, a language evolves, and nothing outside it is doing the work. Bolt on -ig- and you get the causative: somebody makes it evolve. That is the entire content of evoluigi, and it is why you should never learn it as a separate item of vocabulary. La lingvo evoluas, the language evolves. Ni evoluigas la lingvon, we develop the language. Same root, one letter of difference, transitive and intransitive split cleanly down the middle.

The pair to keep straight.

• Evolui - intransitive, no object. La situacio evoluis rapide.
• Evoluigi - transitive, always an object. Ili evoluigis la produkton.

If you can put a thing after the verb, you want the -ig- form. The igi and iĝi article is the full treatment, and this word is one of the cleanest examples in the language.

Where it collides with disvolvi, and how to pick. English "develop" covers both, and Esperanto splits them by picture. Disvolvi at rank 2,595 is literally to unroll something rolled up, so a speaker disvolvas a theme, an argument or a plan: what is inside is already there and is being opened out. Evoluigi is biological and gradual, a thing being brought on over time: a talent, a strain of wheat, an economy, a young player. For a country or an industry either verb turns up in real Esperanto writing, and disvolviĝanta lando is the settled phrase for a developing country. For a photograph, neither: that is riveli.

The rest of the family costs nothing. Evoluo is evolution, evoluigo is the act of developing something, evoluinta is developed and evoluanta developing. All of it comes off the same root, and you learned the root at rank 1,283.