Systemic changes
Internally motivated sound changes may have profound consequences for grammar, as the De Gaulle example above illustrated, and in some cases, what the Neogrammarians identified as analogy repairs the damage, by aligning irregular forms with regular ones.
A good example of analogy is provided by plurals in Old English, the forms of which varied by gender and noun-class, e.g. stanas ‘stones’ (sg. st¯an; masculine) but scipu ‘ships’ (sg. scip, neuter).
As gender and case inflections were lost by the end of Middle English period (stanas > stanes > stones), final s was left as the only plural marker, and was extended to nouns like ship which had formed their Old English plurals in different ways. Something similar is happening with so-called intrusive r in English. Word-final /r/ has been lost from many varieties of English in non-pre-vocalic positions, but not before a following vowel, so a meat lover 
but a lover 
of fine meat. This /r/ at word boundaries has been extended by analogy to many other words which never had /r/ in the first place:
Another important internal process is grammaticalization, by which a full lexical word acquires a grammatical function. An example here is back, which in its original meaning refers to the rear of the human torso, a meaning lost in the complex preposition at the back of, meaning ‘behind’. Similarly, the negative particle pas in French originally had only its full lexical meaning of ‘step’, and was used to reinforce the negative ne with some related verbs, e.g. il ne marcha pas (‘He did not walk a step’). But gradually in negative contexts it lost the meaning ‘step’ and became a general marker of negation, e.g Il ne parle pas (‘He does not speak’, not ‘He doesn’t speak a step’). The loss of lexical meaning that accompanies grammaticalization is known as semantic bleaching; very often phonetic reduction is also involved as the item evolves from lexical to functional unit.
