I usually spend the time in these lessons telling you about all of the amazing aspects of Reed-Kellogg sentence diagramming, but today I'm going to show you one of its limitations.
We're going to diagram a sentence! (Don't worry if you've never diagrammed before. You'll still be able to see the point of this lesson without already knowing how to diagram sentences.)
Bring your attention to how the adjectives an and unexpected are diagrammed.
They are both adjectives, but they have slightly different functions—functions that Reed-Kellogg diagramming doesn't differentiate.
Here is a box illustration that I found helpful. I came across this idea in a diagramming book by Eugene Moutoux.
Unexpected is an adjective modifying the noun gift.
It modifies gift independently.
An is also an adjective, but it's really modifying the noun phrase unexpected gift.
However, we can't show that relationship in Reed-Kellogg diagramming, so we diagram both adjectives an and unexpected in the same way, even though they have slightly different jobs.
Reed-Kellogg diagramming does an amazing job showing how words function in sentences, but remember that diagramming doesn't always do a perfect job of showing the nuances and subtleties of every grammatical relationship.