It depends on the sentence, but it sounds like it's either 'fifty-first century' or 'fifty-first-century' which... the second one looks weird. Whatever. Cite here (http://www.getintouni.com/Free/GrammarStyle/GrammarC/). :)
Either 51st-century pheromones or fifty-first-century pheromones, depending on whether you use numerals for numbers greater than nine or use words (latter is more common in fiction). Reason: entire phrase is a compound adjective modifying pheromones.
Although I don't really think it looks strange without the hyphen - I think that's one of those errors that's so common now things almost look wrong when they're done right.
Particular centuries are spelled out and lowercased.
the twenty-first century the eighth and ninth centuries the eighteen hundreds (the nineteenth century)
Dunno if that's right by Aussie rules, though. *g*
ETA: And of course, the above commenters have the right of it in that there needs to be a hyphen between first and century, as well, since the whole phrase modifies pheromones.
(no subject)
Date: 2009-07-09 11:29 am (UTC)It depends on the sentence, but it sounds like it's either 'fifty-first century' or 'fifty-first-century' which... the second one looks weird. Whatever. Cite here (http://www.getintouni.com/Free/GrammarStyle/GrammarC/). :)
(no subject)
Date: 2009-07-09 06:57 pm (UTC)(no subject)
Date: 2009-07-09 10:36 pm (UTC)I find numerals >9 easier to read than writing it out in words, but am sure the words (with hyphens) are also or perhaps more correct.
(no subject)
Date: 2009-07-09 10:38 pm (UTC)(no subject)
Date: 2009-07-10 05:48 am (UTC)ETA: And of course, the above commenters have the right of it in that there needs to be a hyphen between first and century, as well, since the whole phrase modifies pheromones.
(no subject)
Date: 2009-07-14 02:37 am (UTC)Just sos you know, us Aussies don't think we're too good to use proper English when writing. (speaking, yes) Unlike some countries. *g*