«Преподава́тель(ница)» is someone who teaches students in the university (it roughly overlaps with the English word 'professor'), «учи́тель(ница)» is someone who teaches people in school.
Преподавательница sounds a tad weird. (I know, dictionaries have this word but I guess you have to trust my word here. Or not :)). More generally, even though names of certain professions do have feminine forms, you need to exercise caution using them. Check the notes in the dictionary for разг./разговорное, прост./простонародное, уст./устаревшее and act accordingly.
The second point, it is possible to call a school teacher преподаватель. All it does, it makes your speech sound more formal. The opposite is not true. One cannot call a university professor учитель or учительница, these words are reserved exclusively for school teachers.
> guess you have to trust my word here. Or not
Being a native speaker, I would rather trust my own language intuition, sorry ^^'
Well, in Moscow it does sound weird, about the same as "директорша". Not unheard of but a whole level less useful than учительница
Is the postfix -ель usually equivalent to -er? I've seen it with reader and teacher.
-тель is a fairly common suffix to form a noun that names the object performing an action of a verb. Here are a few examples:
- учитель (the only with the plural in -я)
- выключатель, переключатель
- родитель (quite unusual due to formation from a perfective verb)
It is not the only one, and you should know whether the word exists anyway. The one who buys is покупатель but the one who sells is продавец.
Учитель здесь человекоподобное? Нечто? Неодушевлённое? Уж простите за вопрос, я не эксперт. В школу ходил сорок лет назад, по языку имел крепкий трояк. Объясните, пожалуйста, троечнику.
It looks like учитель has the same root as читать, if so does this mean that, etymologically, a teacher is one who is well-read (educated)?
I’m afraid no, those words are unrelated.
Учи́тель is someone who teaches, it comes from ‘учить’ ‘to teach, to learn’. -уч- in this word in it is a very distant relative of -вык- привыкнуть ‘to get used to’. The -к-/-ч- interchange is still more-or-less alive in Russian, e.g. рука ‘hand’ — ручка ‘little hand, handle, pen’, and вы-/у- interchange is long dead, etymologists can recognise it, but not ordinary speakers.
«Чита́ть» ‘to read’ is related to счита́ть ‘to believe, to think; to count’ and «почитать» ‘to worship, to think highly’. This root originally was used for something like thinking and understanding.
So, etymologically, a teacher is someone who helps you to get used to things, and reading is thinking.