The main categories in German conjugation, like in many other languages, are person, number, tense, mood and voice,
which are represented by inflectional changes in the verb form itself or in an auxiliary verb.
Person and number are always expressed by changes to the form itself: sage, sagst, sagt, sagen (“to say”): fahre, fahst, fahrt, fahren (“to drive”),
whereas the categories of tense and mood are sometimes expressed by changes to itself, for example sagte, ging, fuhr, and sometimes by changes to an auxiliary verb,
the full verb being in the form of the infinitive or past participle, ich werde gehen, ich würde sagen, ich habe gesagt, ich wäre gefahren.
The category of voice is expressed in the passive only by the use of the different forms of an auxiliary, werden (“will”), plus the past participle: das Lied wird gesungen (“The song will be sung”).
The way in which a verb is inflected is determined by the class of verb to which it belongs.
There are two main classes, weak and strong. There is also a small mixed class, made up of verbs that have features of both weak and strong verbs;
a small class that includes the modals (verbs like können – “to be able to” and – müssen – “to have to”); and some irregular verbs (e.g., sein – “to be”).
The majority of German verbs are weak. Weak verbs are regular; they form their past and past participle forms with a -t suffix: lieben - “to love”, liebte –“loved”, geliebt -“loved”.
There are many fewer strong verbs than weak verbs. According to the Duden grammar, there are roughly 170 simple (non-derived) strong verbs in German.
Strong verbs form their principal parts (infinitive, past, past participle) by alternating the vowel of the root: trinken- “to drink”, trank – “drank”, getrunken – “drunk”.
This vowel alternation is known as ablaut, and it can be seen in irregular verbs in English like drink (drink, drank, drunk).
Although there are a number of different ablaut patterns that must be learned in German, the strong verbs appear to be able to resist pressure to become regular (weak),
in spite of their small numbers. Many strong verbs in German, like their strong (irregular) counterparts in English, are very common
(they belong to the basic vocabulary and are used frequently) and are thus relatively stable as strong verbs.
German, unlike English, makes a distinction between the familiar and the polite in second person pronominal forms.
The familiar forms for “you” are du (singular) and ihr (plural). There is one polite form, Sie, which can be singular or plural in meaning.
The third person singular personal pronouns are inflected for gender and are used to refer to objects as well as people.
In English, the “neuter” pronoun “it” can be used to refer to any object. In German, neuter “es” can only be used to refer to objects identified by neuter nouns.
If a noun phrase with a masculine singular noun is replaced by a pronoun, the pronoun must be masculine. This holds for noun phrases with feminine singular nouns as well.
The person and number of the subject of a verb determine the affix that is attached to that verb. Any form of a verb that is inflected for person and number is a finite form.
A form that is not inflected for person and number is a non-finite form.
Non-finite forms are the infinitive (lieben - “to love”); the present participle (liebend – “loving”); and the past participle (geliebt – “loved”, getrunken - “drunk”).
The basic form of a German verb is the infinitive. All German infinitives end in either -en or –n.
Verbs are inflected by attaching affixes to the stem and/or by changing the root vowel of the stem.
The choice of personal pronoun determines the inflectional ending, which must agree with it in person and number.
Thus du, 2nd person, singular, always occurs with the ending -st, ihr, 2nd person, plural, with -t.
German has six tenses: present (Präsens), present perfect (Perfekt), simple past (Präteritum), past perfect (Plusquamperfekt), future (Futur I) and future perfect (Futur II).
The present tense also called the simple present (Präsens) is used to talk about the present and future in German.
We can translate it into one of three English tenses: the simple present, present progressive and future with will or going to.
It is the most commonly used tense in the German language.
The present tense of weak verbs is formed by adding the appropriate person and number endings to the stem of the verb.
Some present tense forms involve the epenthesis of -e-: if a verbal base ends in -d, -t, or in an obstruent followed by a nasal,-e- is added before the endings -st and –t
(e.g. öffnen – (ihr) öffnet (“to open”).
The strong verbs and verbs belonging to the mixed class take the same endings in the present as the weak verbs.
Some strong verbs, however, also change the root vowel in second and third person singular forms.
Most strong verbs with -e- ([e:] or [ε]) in the root change this to -ie- or -i- ([i:] or [i]) in the second and third person singular forms: lesen - du liest, sie liest (“to read”).
Most strong verbs with -a- or -au- in the root umlaut these vowels in the second and third person singular forms: fahren: du fährst, sie fährt (“to drive”).
Perfekt is mostly formed from the appropriate present tense form of 'to have' (haben) and a past participle of the relevant verb placed at the end of the clause.
Some intransitive verbs involving motion or change take 'to be' (sein) instead of haben; this may depend on the exact meaning of the sentence.
Simple past or imperfect (Präteritum), is used to express facts and actions that started and ended in the past.
The past in German is appropriate for narration.
The past is primarily used in written German, a medium that is typical for narrative discourse.
The present perfect, on the other hand, is characteristic of the spoken language.
Weak verbs form the past by simply adding -t to the stem (which yields what we will call the past stem) and then the endings for person and number.
The person and number endings in the past of weak verbs are identical to the person and number endings in the present – with the exception that the third person singular ending is -e
(rather than -t, as in the present) (e.g. liebt-e - “loved”, arbeitet-e – “worked”, öffnet-e – “opened”).
The past of strong verbs is formed by changing the root vowel and adding endings for person and number. The past endings of strong verbs differ from those of weak verbs, however.
In fact, the first and third person singular forms of strong verbs in the past have no endings (e.g. trinken - trank, trank-st, trank, trank-en, trank-t, trank-en (“drank”).
Verbs that belong to the mixed class form the past by changing the root vowel, like strong verbs, but they also add -t to the stem and then the person and number endings of the weak past
(e.g. bringen - brachte - gebracht (“to bring”), brennen - brannte - gebrannt (“to burn”)).
The past perfect or pluperfect (Plusquamperfekt) expresses actions that took place before a certain point in the past. It is the German equivalent of the English past perfect tense.
The future tense (Futur I) is mostly used to express assumptions about the present or future in German. It is formed from the appropriate present tense form of the verb werden (to become) and, as in English, the infinitive of the relevant verb.
The future perfect (Futur II) expresses the assumption that an action will have been completed by the time of speaking, or by a particular point in the future. To conjugate verbs in the future perfect tense, we need the finite form of werden, the past participle of the relevant verb, and the auxiliary verbs sein/haben.
The use of the indicative implies that something is real. It is used to express statements of fact and questions (e.g. - Ich lese die Zeitung. – I’m reading the newspaper).
The main role of the subjunctive is to mark a clause as expressing something other than a statement of what is certain. There are two form of subjunctive in German:
The imperative mood is a mood that is used for expressing commands and also polite requests.
The second person singular imperative form is simply the stem of the infinitive. Verbs with stems that end in -ig, -d, -t, or an obstruent followed by a nasal must also add an -e to the stem.
Strong verbs that change the root vowel in the imperative do not add an -e to the stem.
All other verbs may add an -e optionally (e.g. fahr(e)! –go!, lauf(e)! – run!).
The remaining imperative forms, which are identical with present tense indicative forms, are the following: second person plural, second person polite,and first person plural forms.
Notice that only the polite second person and first person plural forms are accompanied by a personal pronoun (Sie; wir).
In German, prepositions and modifying prefixes are frequently attached to verbs to alter their meaning. Verbs so formed are divided into separable verbs which detach the prefix under certain circumstances and inseparable verbs which do not. The conjugations are identical to that of the root verb, and the position of the prefix for both separable and inseparable verbs follows a standard pattern. The prefix's effect on the verb is highly unpredictable, so normally the meaning of each new verb has to be learned separately.
Verbal prefixation recognizes three types of prefixes: inseparable (prefixes like be- in beschreiben “to describe”), separable (forms like aus- in ausgehen “to go out”),
and variable (forms like über in übersetzen “to translate” and übersetzen “to take across”).
Only those forms that are never stressed or separated from the verbal base are recognized here as prefixes.
These include be-, ent, er-, miss-, ver-, and zer- (traditionally known as inseparable prefixes) and unstressed durch-, über, um-, unter-, and wider-
(the unstressed occurrences of the “variable prefixes”).
Because the so-called separable prefixes and stressed variable prefixes can be separated from their verbal bases, they are treated here not as prefixes,
but as elements of phrasal verbs, like Rad - “bike, wheel” in Rad fahren - “to pedal” and Schlittschuh – “ice skate” in Schlittschuh laufen – “to ice-skate”.
Separable verbs (Trennbare Verben) detach their prefixes in the present, imperfect and imperative. The prefix is placed at the end of the clause. The past participle is the prefix attached to the normal past participle. The infinitive keeps the prefix where it is used, for example in the conditional and future tenses.
The verbs with the following prefixes are separable: ab-, an-, auf-, aus-, bei-, ein-, los-, mit-, nach-,her-, hin-, vor-, weg-, zu-, zurück-.
Inseparable verbs (Untrennbare Verben) retain the prefix at all times. The past participle has the prefix in place of ge- but keeps any irregularities of the root verb's past participle.
The verbs with the following prefixes are inseparable: be-, emp-, ent-, er-, ge-, miss-, ver-, zer-.
A number of verbs are separable with one meaning and inseparable with another.
For example, übersetzen means 'to translate' as an inseparable verb but 'to ferry' as a separable verb.
The verbs with the following prefixes can be either separable or inseparable: durch-, hinter-, über, um-, unter-.
In both English and German, infinitive clauses are a kind of dependent clause in which there is no grammatical subject, only an implied one, and therefore the verb is not inflected. An infinitive clause is particularly dependent on the main clause of the sentence for its meaning. The infinitive, which is combined with "zu" goes to the end of the clause:
If the verb in question has a separable prefix, the zu goes between the prefix and the stem (e.g. anzufangen - 'to begin', zuzumachen - 'to close').
It can be useful to view infinitive clauses as being transformed from main clauses. To make the transition, one drops the subject and converts the finite verb to an infinitive, which goes to the end of the clause.
German uses um ... zu in order to express intention. This construction can usually be translated by "in order to":
ohne ... zu and (an)statt ... zu: there is a further opportunity to use infinitive clauses in German where English builds prepositional phrases with gerunds.