Why it's hard to say you're "fluent"

Here are some things Grace can say, at 2, that I don't know how to say in Spanish, in spite of years speaking and teaching the language:

* Jellyfish
* Reindeer
* Futon

Okay, that's my whole list for now, but the point is, vocabulary comes in strange ways. There are probably hundreds of words your average Spanish-speaking four or five year old knows that I don't know, even though I am basically fully conversant and of course have all of the educated vocabulary five year olds don't have. Words for plants and animals (which, oddly, seem so much important in toddlerdom than adulthood), words for parts of cultural rituals, and on.