"Ten days HAVE passed", but "Ten days IS a long time". Why? A question for fellow English native-speakers... "Ten days HAVE passed" (plural) "The ten days WERE fun" (plural) "Ten days IS a long time to wait" (singular) "Ten days IS the limit" (singular) A non-native speaker asked me why verb's singular in the second two, given the subject is plural. I was stumped, and had to say "because the object feels singular". Not a very useful explanation! However *"the ten days WAS fun" or *"Ten days ARE a long time" definitely sound wrong to my ears. How would you explain this? Is it related to the the transitivity of "be"?