Personal pronouns—in particular, clitic pronouns—show the greatest variation across the Romance languages. Modern varieties and historical vernaculars exhibit a kaleidoscopic degree of variation with respect to several syntactic parameters (placement, climbing, doubling, interpretation, etc.). Despite the apparent chaotic variation, some descriptive generalizations can be established on the basis of a rich and growing array of data.
The Romance languages are characterized by the existence of pronominal clitics. Third person pronominal clitics are often, but not always, homophonous with the definite determiner series in the same language. Both pronominal and determiner clitics emerge early in child acquisition, but their path of development varies depending on clitic type and language. While determiner clitic acquisition is quite homogeneous across Romance, there is wide cross-linguistic variation for pronominal clitics (accusative vs. partitive vs. dative, first/second person vs. third person); the observed differences in acquisition correlate with syntactic differences between the pronouns. Acquisition of pronominal clitics is also affected if a language has both null objects and object clitics, as in European Portuguese. The interpretation of Romance pronominal clitics is generally target-like in child grammar, with absence of Pronoun Interpretation problems like those found in languages with strong pronouns. Studies on developmental language impairment show that, as in typical development, clitic production is subject to cross-linguistic variation. The divergent performance between determiners and pronominals in this population points to the syntactic (as opposed to phonological) nature of the deficit.