Adjectives

Adjectives agree with the noun they qualify in case, number, and gender. Adjectives evolved into strong and weak declensions, originally with indefinite and definite meaning, respectively. As a result of its definite meaning, the weak form came to be used in the daughter languages in conjunction with demonstratives and definite articles. The terms "strong" and "weak" are based on the later development of these declensions in languages such as German and Old English, where the strong declensions have more distinct endings. In the proto-language, as in Gothic, such terms have no relevance. The strong declension was based on a combination of the nominal /a/ and /ō/ stems with the PIE pronominal endings; the weak declension was based on the nominal /n/ declension.

Determiners

Proto-Germanic had a demonstrative which could serve as both a demonstrative adjective and a demonstrative pronoun. In daughter languages, it evolved into the definite article and various other demonstratives.

Verbs

Proto-Germanic had only two tenses (past and present), compared to the six or seven in Greek, Latin, and Sanskrit. Some of this difference is due to deflexion, featured by a loss of tenses present in Proto-Indo-European, for example the perfect. However, many of the tenses of the other languages (future, future perfect, probably pluperfect, perhaps imperfect) appear to be separate innovations in each of these languages, and were not present in Proto-Indo-European.^{[citation needed]}

The main area where the Germanic inflectional system is noticeably reduced is the tense system of the verbs, with only two tenses, present and past. However:

• Later Germanic languages (for instance Modern English) have a more elaborated tense system, derived through periphrastic constructions.

• PIE may have had as few as three "tenses" (present, aorist, perfect), which had primarily aspectual value, with secondary tensal values. The future tense was probably rendered using the optative and/or desiderative verbs. Other tenses were derived in the history of the individual languages through various means (originally periphrastic constructions, such as the augment /e-/ of Greek and Sanskrit and the /-b-/ forms of Latin, derived from the PIE verb /bʱuː/ one form of verb "be"; reinterpretation of subjunctive and desiderative formations as the future; analogical formations).

Verbs in Proto-Germanic were divided into two main groups, called "strong" and "weak", according to the way the past tense is formed. Strong verbs use ablaut (i.e. a different vowel in the stem) and/or reduplication (derived primarily from the Proto-Indo-European perfect), while weak verbs use a dental suffix (now generally held to be a reflex of the reduplicated imperfect of PIE *dheH₁- originally "put", in Germanic "do"). Strong verbs were divided into seven main classes while weak verbs were divided into five main classes (although no attested language has more than four classes of weak verbs). Strong verbs generally have no suffix in the present tense, although some have a -j- suffix that is a direct continuation of the PIE -y- suffix, and a few have an -n- suffix or infix that continues the -n- infix of PIE. Almost all weak verbs have a present-tense suffix, which varies from class to class. An additional small, but very important, group of verbs formed their present tense from the PIE perfect (and their past tense like weak verbs); for this reason, they are known as preterite-present verbs. All three of the previously mentioned groups of verbs—strong, weak and preterite-present—are derived from PIE thematic verbs; an additional very small group derives from PIE athematic verbs, and one verb *wiljanaN "to want" forms its present indicative from the PIE optative mood.

Proto-Germanic verbs have three moods—indicative, subjunctive and imperative. The subjunctive mood derives from the PIE optative mood. Indicative and subjunctive moods are fully conjugated throughout the present and past, while the imperative mood existed only in the present tense and lacked first-person forms. Proto-Germanic verbs have two voices, active and passive, the latter deriving from the PIE mediopassive voice. The Proto-Germanic passive existed only in the present tense (an inherited feature, as the PIE perfect had no mediopassive). On the evidence of Gothic—the only Germanic language with a reflex of the Proto-Germanic passive—the passive voice had a significantly reduced inflectional system, with a single form used for all persons of the dual and plural. Note that, although Old Norse has an inflected mediopassive, it is not inherited from Proto-Germanic, but is an innovation formed by attaching the reflexive pronoun to the active voice.

Although most Proto-Germanic strong verbs are formed directly from a verbal root, weak verbs are generally derived from an existing noun, verb or adjective (so-called denominal, deverbal and deadjectival verbs). For example, a significant subclass of Class I weak verbs are (deverbal) causative verbs. These are formed in a way that reflects a direct inheritance from the PIE causative class of verbs. PIE causatives were formed by adding an accented suffix -éi̯e/éi̯o to the o-grade of a non-derived verb. In Proto-Germanic, causatives are formed by adding a suffix -j/ij- (the reflex of PIE -éi̯e/éi̯o) to the past-tense ablaut (mostly with the reflex of PIE o-grade) of a strong verb (the reflex of PIE non-derived verbs), with Verner's Law voicing applied (the reflex of the PIE accent on the -éi̯e/éi̯o suffix). Examples:

• *bītanaN (I) "to bite" → *baitijanaN "to bridle, yoke, restrain", i.e. "to make bite down"

• *rīsanaN (I) "to rise" → *raizijanaN "to raise", i.e. "to cause to rise"

• *beuganaN (II) "to bend" → *baugijanaN "to bend (transitive)"

• *brinnanaN (III) "to burn" → *brannijanaN "to burn (transitive)"

• *frawerþanaN (III) "to perish" → *frawardijanaN "to destroy", i.e. "to cause to perish"

• *nesanaN (V) "to survive" → *nazjanaN "to save", i.e. "to cause to survive"

• *ligjanaN (V) "to lie down" → *lagjanaN "to lay", i.e. "to cause to lie down"

• *faranaN (VI) "to travel, go" → *fōrijanaN "to lead, bring", i.e. "to cause to go"

• *faranaN (VI) "to travel, go" → *farjanaN "to carry across", i.e. "to cause to travel" (an archaic instance of the o-grade ablaut used despite the differing past-tense ablaut)

• *grētanaN (VII) "to weep" → *grōtijanaN "to cause to weep"

• *lais (I, preterite-present) "(s)he knows" → *laizijanaN "to teach", i.e. "to cause to know"

As in other Indo-European languages, a verb in Proto-Germanic could have a preverb attached to it, modifying its meaning (cf. e.g. *fra-werþanaN "to perish", derived from *werþanaN "to become"). In Proto-Germanic, the preverb was still a clitic that could be separated from the verb (as also in Gothic, as shown by the behavior of second-position clitics, e.g. diz-uh-þan-sat "and then he seized", with clitics uh "and" and þan "then" interpolated into dis-sat "he seized") rather than a bound morpheme that is permanently attached to the verb (as in all other Germanic languages). At least in Gothic, preverbs could also be stacked one on top of the other (similar to Sanskrit, different from Latin), e.g. ga-ga-waírþjan "to reconcile".