“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 (see Case study below).”