Why is 登録した the past tense of 登録?


I am just a beginner, and I am reading Tae Kim's _Guide to Japanese_. My
questions are:

  1. Why is the past tense of 登録, 登録した?

  2. Is 登録 (register) a noun or a verb?

  3. In the following example, the word should be a verb, right? If it is a verb, it is ru-verb or u-verb? メールアドレスを登録した。 Registered email address.

  4. (This question is not related to any questions above and the topic) By the way, what is the best English-Japanese dictionary? Also, how can I know if a word is a noun, i-adjective, na-adjective, u-verb, ru-verb, or an exception?




  1. 登録 does not have a past tense because it is a noun (meaning registration). It can be made into a verb by adding する. 登録する means 'to register', so naturally the past form would be 登録した. Many nouns can be turned into verbs by adding する.

  2. As above, 登録 is a noun. It cannot possibly be a verb because there is no way to conjugate it. All verbs must end in a kana from the u-group.

  3. So I think ru-verbs and u-verbs are godan and ichidan verbs, right? する is neither. It is somewhat irregular.

  4. For the level you seem to be at right now probably jisho.org would be a good choice of dictionary. If you look up [登録](https://jisho.org/search/%E7%99%BB%E9%8C%B2%20) you'll see that it is labeled as both a noun and a suru verb.

As for how to distinguish between the different types of word, I could spend a
lot of time telling you, but I think it is pointless. It will become clear to
you very quickly. And you can always use a dictionary.

More generally, if you have got to the stage of reading something like
メールアドレスを登録した and don't know anything about する then I think you need to step
back a bit. You have missed some very important material somewhere along the
way.

