Putting た in i-adjectives?


I was looking at a jisho.org example sentence for [軽]{かる}い, and I was a bit
confused about **[重]{おも}たそう**.

> えりのスーツケースは **[重]{おも}たそう** だが、[実際]{じっさい}はとても[軽]{かる}い。  
> Although Eri's suitcase looks heavy, it's actually very light.

I figured out that そう was for "looking like," but the た confused me... I then
learned that [重]{おも}たい is just another form of [重]{おも}い. During my research, I
found another adjective like this from a Maggie Sensei lesson:
[眠]{ねむ}い／[眠]{ねむ}たい.

So now I'm wondering two things:

  1. What are the differences between the adjectives ending in い and たい?
  2. Do all i-adjectives have such a pair?

Thank you.




  1. I can only answer based on your examples, but, at least for them, I think the "ta"-versions emphasize that the property (e.g. heavy) is "a problem", i.e. is something "negative" (=omotai since it's hard to carry), so most likely that is valid also for other similar ones, assuming they exist.

  2. No, far from all, I think they are very rare. Omotai is used often. IMHO nemutai a lot less. At least now I can't come up with other examples.

