Politeness Levels
“Be polite; write diplomatically; even in a declaration of war one observes the rules of politeness.” – Otto Von Bismark
You probably already noticed this (and knew this because of previous grammar points you’ve learned), but the verb in the first part of the sentence (the action you’re nominalizing) is always casual form.
a かんじ を よむ の は かんたん です。
a かんじ を ならう の は むずかしい です。
The よむ and ならう verbs (i.e. the ones getting nominalized) are both in casual form (dictionary form) and always will be. The stuff that comes after can be anything, though that depends on how casual / formal you want to be. The above sentences are neutral/formal sentences because the ending is neutral formal. Want to make the sentences casual? Then you’d do this:
a かんじ を よむ の は かんたん だ。
a かんじ を ならう の は むずかしい。
If you remember from before, na-adjectives (like かんたん) are made casual by ending them with だ instead of です. i-adjectives, on the other hand, are made casual by dropping the です entirely. That’s exactly what we did in the examples above. So, what decides the casualness or the formalness is the thing at the end, not the action you’re nominalizing. The nominalized verb is always dictionary form.
Before you move on, make sure you know that. Next, we’re going to look at different tenses – it’s probably exactly what you expect, too.