Hi everyone
I have a quick query regarding some english words that are derived from latin, those that end in cide (homicide, pesticide etc). For example, I know that the stem of the word genocide is derived from genus, but is the cide part derived from a latin word? one meaning ‘to kill’ perhaps?
Thanks in advance for any help
Ironic Lettuce
PS what does QED stand for and mean?
yes, the latter part of those compounds comes from caedo -ere, cecidi, caesum, which had the literal meaning of ‘cut’ or strike’, but of course was commonly used of ‘killing’ or, worse still, ‘cutting one to pieces’.
~D
I’ll have to look around my dictionary a bit for the -cide suffix.
QED: Quod erat demonstrandum, that which was shown is used at the end of a detailed argument, or proof in suppoprt of the conclusion.
thanks both! very helpful 
thanks again
IL
Slight correction:
QED = quod erat demonstrandum = which was to be shown, i.e, this is what we had to prove
Hmm.. Off topic question:
I’ve only ever seen the passive periphrastic in the present tense(with est) because it’s considered more ‘advanced’ than what I’m supposed to know. How exactly would you translate the following? (I’ll put my guesses)
amandum erat (had to be loved)
amandum erit (will have to be loved)
amandum fuit (had to be loved)
amandum fuerat (had had to be loved?)
amandum fuerat (will have had to be loved?)
Also, can you use the passive periphrastic with other persons and numbers of esse? (e.g. amandi sumus)
Vale,
Titus Marius Crispus
Basically, yes (assuming the last one is fuerit). Some of these are quite rare, especially beloved by those cryptic medieval scholars. If you should ever have to translate one that sounds incredibly awkward, effort should be taken to smooth out the English afterwards.
Also, can you use the passive periphrastic with other persons and numbers of esse? (e.g. amandi sumus)
Yes indeed. It can also be found in the subjunctive and even infinitive - try translating that 
Ok, I got lost here.
Quod erat demonstrandum
I thought this was a pluperfect passive participle form. (BLD §202)
But when I looked up demonstrandum:
dēmonstro, -āvi, -ātum, to show,
I can’t see how the ending is formed. Nor can I see an infinitive form.
What happened?
infinitive forms often aren’t listed in dictionaries.
demonstrandum is from demonstro but rather than being a pf past ptcpl is a so-called gerundive, which are typically formed with the verbal stem and -andus, -a, -um which declines as a standard adjective. it has various senses, including that of obligation in the nominative.
~D
Tim, I believe you are using BLD? He explains this with the other participles on Pages 161-164.
If a verb looks like first conjugation then it probably is first conjugation. My dictionaries just put demonstro (1), to show it is of the first conjugation, but leave it to dictionary writers to just do their own thing…
Whew! Thanks! I thought this was beyond my current knowledge.
I was worried that I had lost my marbles and was reading the “New Latin”