Grimm's Law describes the change that occurred in the phonological system of the Indo-European language during its transition towards the Germanic dialect; this is the main characteristic of Germanic Language family so it defines the languages that belong to this family. This process solved an anomaly in the organization of the consonant system; it consisted of nine plosives and only one fricative. The process described by Jacob Grimm transforms the phonological organization to establish a new system with six plosives and seven fricatives. Phonological changes occurred in order as it follows. It is the only possible order, since if voiced plosive would have become voiceless firs, they would have been transformed in fricatives; we would have a word like **diufs (incorrect).
Voiceless plosives became voiceless fricativesp,t,k/→f ,Ө, x/.
Lat. Pater - OE fӕder/ O.N. faδir.
Lat. Tres - OE Ϸrēo/ O.N. Ϸrir.
Lat Cor - OE heorte/ O.N. hjiarta.
Voiced plosives became voicelessb, d, g/→p,t,k/.
Lith dubūs - OE dēop (deep)/ Go diups/ O.N. djupr.
Lat. edō - OE etan (eat)/ Go itan.
Lat. Ego - OE ic (I)/ ON ek.
Aspirated voiced plosive became voiced fricativebᵸ,dᵸ,gᵸ/→β,δ,ϒ/. This last change was obscured because they became plosive before the historical periodb, d, g/.
Skt. bhrātar – OE brōδor/ ON broδir/ Go brōϷar.
Greek thugater – OE dohtor/ ON dóttir.
Skt hamsa (IEgᵸ/→Skth/) – OHGerm gans/ OE gōs (goose).
Verner's Law and Accent Shift is a process described by Karl Verner that explains the anomalies of the Grimm's Law. Verner highlighted the fact that Grimm's Law did not operated regularly in the case of voiceless plosives when the accent of the IE word followed the consonant. In that casep,t,k/ became voiced fricativesβ,δ,ϒ/. This is why we don't find the expectedӨ/ in the second syllable in the word fӕder (lat. pater; Sk. pitar). Changes described by Verner had been obscured by the Germanic systematic word-initial stress, called Germanic Accent Shift.