Past verbs

You form the past tense of a verb by attaching た or だ to a specific "stem".

Stems are important for godan verbs because godan verbs have many stems and often present irregularities.

90% of the time, you only use three stems. Here's an example:

Note: “a” form and “i” form aren’t real terms, it’s just an example to show the sound vowel these stem end as. We don’t need to know the Japanese linguistic names of these forms now, but you can look them up if you want.

Here's an example of these stems in use:

殺す
He kills

殺さない
He doesn't kill

殺した
He killed

That's right. Basic stuff like tense and negation uses only three stems. There are more stems, but they show up less often. We'll cover them later.

With that out of the way, we can introduce the past tense properly. We've seen the past tense forms of だ and です already, which are だった and でした. We also saw 殺した in the stem example above.

You'd be right to assume that the た is what makes it the past tense. The hard part is that the stem for the past tense of godan verbs isn't as regular as the stem for the negative form. It depends on the original syllable ending of the plain form. Here are all possibilities:

切る	殺す	死ぬ	選ぶ	読む	買う	動く	急ぐ	持つ
切った	殺した	死んだ	選んだ	読んだ	買った	動いた	急いだ	持った

Don't memorize this table. There's a rule for this: replace the "u" vowel with an "i" vowel, so you get like 切り, 殺し, etc. then attach the た after it. However, there are exceptions to this “rule”:

• if the verb ends with ぬ or a voiced kana (ぶ or ぐ) た becomes だ.
• if the verb ends with う, つ, or る the “i” stem becomes っ and doubles the following た sound (買う -> 買った, etc)
• if the verb ends with ぬ, ぶ or む, the “i” stem gets “slurred” and it becomes ん (選ぶ -> 選んだ)

There are also a couple of verbs with a funny irregular conjugation, for example 問う becomes 問うた. There are only a few of them that behave like this (乞う -> 乞うた being another one). You don’t need to memorize these, just be aware they exist, they are not very common.

Japanese speakers don't go through this mental process whenever they conjugate something. This process is like trivia to them. At the very least, if you do a little reading and listening in Japanese, you will be able to recognize the past tense at a glance. Exposure is more powerful than memorization.

The past tense of ichidan verbs is easy. Just replace the る with a た.

We will learn another use of this stem, in Lesson 12.

The rules of verb conjugations are more complicated than this, but take this one step at a time.