What suffix do you add to a verb to make it perfective or imperfective?

Question

What suffix would be added to the end of a verb to make as it is being done (I'm eating), or that it has been done (I have eaten, I've ate). For example 私は食べる, or I eat, 食べる would be converted into what to make it, I have eaten and I'm eating?

Answer 1

In general, trying to translate specific sentences from English into Japanese isn't the best way to learn Japanese grammar (although it can be part of a greater experience). Japanese grammar doesn't work exactly the same as English grammar and has different "building blocks", so things don't always translate directly over. Nevertheless, here are how you would do the progressive and perfect in Japanese.

Progressive

The progressive aspect in English has a pretty direct equivalent in Japanese. Namely, it is the 〜て form of the verb followed by the auxiliary verb いる (note, the い is commonly dropped). In the case of たべる it would be たべている.

Here is a full derivation for たべる (tabe-ru):

taberu in progressive aspect
= {progressive == 〜て form + いる}
(taberu's 〜て form)iru
= {て form == verb stem + て}
tabeteiru

Here is a derivation of something with an uglier 〜て form for fun, かく (kak-u):

kaku in progressive aspect
= {progressive == 〜て form + いる}
(kaku's 〜て form)iru
= {て form == verb stem + て}
*kakteiru
= {k+consonant == i+consonant (イ音便)}
kaiteiru

Perfect

The perfect aspect in English is one of those things that does not have a direct equivalent in Japanese grammar. So, to figure out how to translate the perfect, we need to break down what the perfect is used for in English by meaning:

• To denote something that happened before now. In this case, "I have eaten" is semantically equivalent to "I ate" in English. In Japanese, we use the past tense for this: たべた. The past tense in Japanese is to add 〜た to the stem, which generally requires phonological corrections for -u verbs, just like with the 〜て form.

  taberu in past tense
  = {past == verb stem + た)
  tabeta

  kaku in past tense
  = {past == verb stem + た)
  *kakta
  = {k+consonant == i+consonant (イ音便)}
  kaita

• To denote experience with something. For example, "I have skydived." In this case, just as you can't say "I skydived." to mean this in English, the past tense would not mean this in Japanese. Instead, we use the construction (past tense of verb)+ことがある. So in this case,

  show experience of sukaidaibingu wo suru
  = {experience == past tense + ことがある}
  (past tense of sukaidaibingu wo suru) + koto ga aru
  = {past tense of する == した}
  sukaidaibingu wo shita koto ga aru