kristanismo

Built from the adherent, not from the founder. Kristanismo is kristano plus -ism-, so the literal reading is the -ism of Christians. That is one step further out than English goes: Christianity is built on Christ, while Esperanto builds on the follower. Take the chain apart and every link is one you already own. Krist- is the name. -An- means a member of a group, giving kristano, a Christian. -Ism- makes the doctrine, giving kristanismo. And kristana is the adjective, from the same middle step.

The asymmetry is worth noticing rather than tidying. Islamo is the religion, islamano a Muslim, islama Islamic - -an- doing its ordinary job outward from a religion-word. Kristanismo runs the other way, building the doctrine on top of the adherent. Judo is a plain root for the person, with juda and judismo around it. Nobody planned this; it is what happens when words arrive at different times from different languages. The countries and peoples article works through the whole -an- machine, from continents down to villages, and this is one of its stranger corners.

-Ism- in Esperanto. The suffix was not in the original Fundamento - it was made official in 1919 - and it does exactly what its international counterpart does: it names a doctrine, a system, a movement or a habit of thought. The course has now taught rasismo, kapitalismo, egoismo and this one, and the pattern is productive, so esperantismo (the idea behind the language) and internaciismo are ordinary words rather than coinages. The matching -ist- gives the person: kapitalisto, esperantisto, egoisto.

One decoy in the same shape. Abismo, an abyss, ends in the same four letters and contains no suffix at all - it is one Greek root, and there is no ab- to cut it from. Check that the piece in front of -ism- is a word before you trust the seam.

Register. This is an encyclopedic word, not a devotional one, and it takes the definite article in the ordinary Esperanto way when you mean the religion as a whole: la kristanismo. Neighbouring vocabulary: eklezio is the Church as an institution, preĝejo the building, religio the general category, and kredi the verb, whose noun kredo is the belief itself.