Words sometimes mislead us about their origin. On occasions, the root of words may lead one to think that they come from the same family, but this not always the case.
There are three words that come from Latin that are very similar phonetically and semantically, akin in their structure and with very close meanings that may even overlap, such as sector, sect and secession.
They all look alike, don’t they? They all start with se and contain the letters c and t that mark their structure. And they have clearly similar meanings.
Sector (section): means a part of a whole. It is the result of dividing something into smaller parts. Anything can be divided into sections: geometric shapes (circular sector), cities, companies, the market, the battlefront... it can be used for everything.
Sect: a group of people, separated from the rest of society, who share a common belief (usually religious). It immediately brings to mind the idea of separation, of someone separate from the rest, of division, of a group that thinks differently.
Secession: the separation of a part of something to split into two. Especially used to talk about two parts of a country that separate and form different countries.
Although these words seem to be from the same family, in reality they deceive us. They are completely different words, which come from three Latin roots that have nothing in common with each other.
Sector comes from secare, i.e., to cut, separate or divide. That is where secant, segment, sex, insect and science (from scrire) come from, amongst others,
Sect comes from the Latin secta, which in turn comes from sequi an irregular deponent verb that means to follow or accompany. It refers to people who follow the same idea, leader or belief. People who are the followers of someone or something. Sequi is the root of second, sequel, sectarian, pursue, prosecute, obsequious, persecute, sequence, non-sequitur, subsequent, society, etc. It is not surprising that it causes confusion, because in Latin secta (sect) comes from the participle secutus. And by coincidence, secta is also a (supine) form of the verb secare.
Finally, secession comes from the Latin verb cedere, which means to leave or withdraw, with the prefix se that adds the meaning of separation (segregate, sedition, secret). It thus means to leave, to walk along separate, different paths. Words like accede, concede, exceed, precede, proceed, recede, secede, etc. all come from the same root (cede).