When you look up a verb in a dictionary, you see something like this:
to go | 가다 |
to speak | 말하다 |
to be good | 좋다 |
to read | 읽다 |
Let’s call this the “dictionary form” of a verb. The stem of the verb is what you get when you take away the 다. You'll be putting your verb endings onto this stem.
Note that the verbs to be good and to read have stems that end in a consonant; the other two stems end in a vowel. This is an important distinction.
The process of adding endings to the verb stem is called conjugation. Before we can start conjugating, we need to know whom we’re talking to.