blasfemi

A precise word, not a general one. Blasfemi is to speak against what is held sacred - a god, a scripture, a holy person or thing. It is not a synonym for swearing. English lost that distinction some time in the nineteenth century and now uses blasphemous loosely for anything shocking; Esperanto keeps it narrow, and the register is legal, theological and encyclopedic rather than conversational.

The fence around swearing. Profanity in the ordinary sense - the words people say when they drop something - is sakri, a root this course has not yet reached, and the milder everyday verb is insulti, to insult, which is aimed at a person rather than at anything holy. Malbeni, to curse, is different again: it means to call down harm, and it is a religious act rather than a rude one. So there are four separate verbs, and using blasfemi for a stubbed toe would be a genuine misunderstanding rather than a stylistic slip.

English blame is the same word, worn down. Church Latin blasphemare became Old French blasmer and then English blame, losing three syllables and all of its religion on the way. The learned form was borrowed again later, which is why English has both blaspheme and blame from one Greek verb - a doublet of exactly the kind the false friends article collects.

Grammar and family. Blasfemo is the utterance, blasfemulo a person who makes a habit of it, blasfema the adjective. The verb is transitive with an object (blasfemi la nomon de Dio) and intransitive with kontraŭ (blasfemi kontraŭ la sanktuloj); both are attested and neither is wrong. The religions article, Esperanto kaj religioj, sets out the wider vocabulary and the movement's long, complicated relationship with the churches.