German Imperfect Tense
Its use: Like English, German has more than one past tense. The Imperfect [sometimes called the simple past] can be used to describe any event/action in the past (e.g. made, did make, has made, was making, used to make), and has pretty much the same meaning as the Perfect Tense. It's used more in written German (so you find it a lot in newspapers and short stories, for example), but sometimes occurs in spoken German also, especially the German verbs hatten (had) and waren (was/were).
Form: The Imperfect Tense has one verb part (the Perfect has two parts: e.g. Ich habe ihn gesehen = I have seen him).
Weak verbs: add these endings (highlighted red) to the stem of the verb.
How do you know if it's a weak verb or a strong verb? Look for the verb in the Table of Strong Verbs. If it's not there, it's most likely a weak verb, and you use the endings given above.
Strong verbs: They're in the Table of Strong Verbs. The stem vowel of many strong verbs changes in the Imperfect (in English also - I begin, I began) and you have to learn them. The column headed Imperfect Tense in the table gives the verb form you use with ich and with er/sie/es. For the du form, add -st to that. For the wir form, and sie (they), and Sie (formal you), add -en. For ihr, add -t.
For example: ich schwamm, du schwammst, er/sie schwamm, wir schwammen
Remember that the ich form and the er/sie/es form are the same as each other, and that the wir and sie (they), and Sie (formal you) forms are the same as each other.
Some verbs whose stem ends in -d or -t have an extra e before the Imperfect endings are added, e.g. ich arbeitete.
Explanations and examples at other sites:
An explanation by Dartmouth University USA of the Imperfect Tense
Imperfect Tense exercise - weak verbs (D Nutting)
Imperfect Tense exercise - strong verbs (D Nutting)
Created by D Nutting