Wondering why Apple spell checker doesn’t know the word – "Yay"!

When I wrote an e-mail to my friend, I found “Yay” is not listed in Apple’s dictionary. The red dash line was an eyesore to me.

Even though the third-party’s English-Japanese/Japanese-English one, Mac OS X’s built-in dictionary seems to recognize this word. Anyway, pressing and holding Apple+Control+D is very useful. This means I don’t have to use the SPACE ALC Bookmarklet I have developed before. Yay