I am no spelling whiz or grammar genius, so I rely heavily on software tools like Microsoft Word and OS X's built-in system wide spelling and grammar checking. Word I believe was the first to implement spelling and grammar checking as you type, for me it was a huge innovation. OS X's built-in spell check nearly anywhere you type text, especially on the Web in Safari, was one of those extremely nice surprises coming from Windows years ago. It is one of those "why isn't this in Windows" features.
Mac OS X 10.5 Leopard added English Grammar checking as you type. When I saw this on the Leopard Feature List (pictured left), I was extremely excited about having a system wide grammar checker. I was really looking forward to having this functionality in Mail.app, problem was, I am embarrassed to admit I couldn't figure out how to use it. But I figured it out now, here's what I am talking about.
Turn it on
Grammar check is supposed to be on by default as you type, but it seems to depend on the app. If you want to make sure it's on, you have to right click in a box you enter text, then click on Spelling and Grammar, then finally make sure Check Grammar With Spelling is checked.
Make Mistakes, Get Suggestions
Here is a sample sentence that the OS X Grammar checker flags:
I had always expected that you should right-click on any of the words with the green underline to see grammar suggestions, just like in Microsoft Word. In Mail.app, this isn't what happens. When you right-click in Mail, you see the menu on the left without suggestions. When Leopard first shipped, I thought this surely must be just a bug and kinda forgot about it. Then today something unexpected happened. I hovered over the grammar text by accident, which you then get to see a tooltip like this:
So you can use the tooltip, but I also found that their is a floating Spelling and Grammar tool window:
But What If Mail.app Is Broken in 10.5.0 - 10.5.5
Seeing the tooltip I thought Mail.app's behavior must be by design, but after playing around some more, I don't think that is the case. I use MarsEdit to write my blog posts, and since it's a Mac OS X app, the place where I type my content is the same OS X text area that does automatic spell checking. I didn't remember ever seeing grammar checking while typing, so I went and turned that on and typed my sample sentence:
Bob said better to be feared than respected, with regards to investing in stocks.
Sure enough, with regards to was highlighted as having faulty grammar. I right-click, and there are suggestions on the right-click menu as pictured on the left! Tough to draw a conclusion, Mail could intentionally (by design) or unintentionally (bug) not be showing grammar suggestions on the right-click menu. I filed a bug on it, #6319745 in RadarWeb (and I hope Radar, but I don't have access to the actual app).