Characteristics, Writing and Classification

Germanic became different from the other Indo-European language groups in seven main ways: 
1.
The Indo-European verbal system was simplified. Indo-European distinctions of tense and aspect were lost except for the present and preterite (past) tenses.
 
2
. Germanic developed a preterite tense (called weak or regular) with a dental suffix, -d or -t (e.g. fish, fished, etc.). Germanic languages thus have two types of verbs, weak (regular) and strong (irregular). Strong verbs indicate tense by an internal vowel change (e.g. swim, swam, swum). Modern English has 161 strong verbs; all are of Germanic origin.) The weak form is the living method of inflection, and many originally strong verbs have become weak.
 
3.
Germanic developed weak and strong adjectives: different sets of inflectional endings for adjectives depending on the definiteness of the noun phrase. Modern English adjectives don't inflect at all, except for the comparative and superlative; this was not the case in Old English, where adjectives were inflected differently depending on whether they were preceded by an artic1e or demonstrative: pa geongan ceorlas 'the young fellows' and geonge ceorlas 'young fellows.' (The weak adjective ends in –an while the strong adjective ends in -e.)
 
4. The Indo-European free accentual system allowed any syllable to be stressed. In Germanic the accent (or stress) is mainly on the root of the word, usually the first syllable.5. Several Indo-European vowels were modified in the Germanic languages. Indo-European /a:/ became /0:/. Compare Latin mater and Old English modor. 
6. Two consonant shifts occurred in Germanic. First Sound Shift (commonly known as Grimm's Law). He formulated a formula describing the regular changes undergone by Indo-European stop consonants represented in Germanic. Essentially, it states that Indo-European p, t, and k be come Germanic f, th, and h; Indo- European b, d, and g be come > Germanic p, t, and k; and Indo-European bh, dh, and gh be come Germanic b, d, and g.
The Second Sound Shift (also known as the High German Sound Shift) affected the high but not the low Germanic languages, so English was not affected.
7.  Germanic has a number of unique vocabulary items, words which have no known cognates in other Indo-European languages. These words may have been lost in the other Indo-European languages, borrowed from non-Indo-European languages, or perhaps coined in Germanic. Among these words are Modern English rain, drink, drive, broad, hold, wife, meat, fowl.
Germanic languages differ from each other to a greater degree than do some other language families. They differ in how conservative or how progressive each language is with respect to an overall trend towards analycity. Some, like German and Dutch, have preserved much of the complex inflectional morphology inherited from the PIE. Others, like English have moved towards a largely analytic type.

Writing
The earliest evidence of Germanic comes from names recorded in the 1st century by Tacitus, but the earliest Germanic writing occurs in a single instance in the 2nd century Be. Early runic inscriptions are al so largely limited to personal names, and difficult to interpret. Later, Christian priests and monks who spoke and read Latin in addition to their native Germanic varieties began writing the Germanic languages with slightly modified Latin letters. In addition to the standard Latin alphabet, various Germanic languages use a variety of accent marks and extra letters, including umlauts, the B (Eszett), IJ, 0, lE, Á, A, O, D, 3, and p and P; from runes.

 
Classification

Divisions between subfamilies of Germanic are rarely precisely defined. Tree of Germanic Languages: