'Conjecture' is a verb as well as a noun. But I'll admit it sounds weird — by French inflection one would expect "I conject", which seems to be obsolete...
Yep. Dictionary.com calls it obsolete. Webster wants me to pay, and OED can't find it.
conject
late 14c., obs. verb replaced by conjecture (v.). Also in form congette.
my concise oxford dictionary (dead tree, c 1984) lists conjecture as a verb (not marked as obsolete).
It's the word "conject" that's obsolete, not "conjecture".
oh, sorry, mis-followed the conversation.
I believe so.
Very common in mathematical circles. Actually, the entire first page of Google's results for "we conjecture that" appears to be math.