Why are some words highlighted in yellow?
At first I thought that a highlighted word was a word that was not shown before but then I saw a word I was sure I didn't know and it was not highlighted. So now I'm curious. Most of the words are in gray but every once in a while there will be a yellow word… what does this mean?
Highlighted words are supposed to be new words. Some words are foreshadowing though, they'll be introduced in later lessons. Those one's won't be highlighted.
Like Usagiboy says, the highlighted words are supposed to be the new ones, but it doesn't always work exactly as it should. I've had exercises come up with personal pronouns highlighted halfway down the tree 8-o technology is not perfect.
Don't worry about it ;)