I-VI -- Introducing the frequency debate in studies of language acquisition -- Opening statement -- What frequency can do and what it can't -- The acquisition of determiners -- The role of input frequency in article acquisition in early child Swedish -- Testing the effects of frequency on the rate of learning: Determiner use in early French, German and Italian -- Input frequencies across development -- The acquisition of non-agent subjects in child Hebrew: The role of input -- The role of input frequency in early language production: Children's usage of Serbian prepositions -- Characteristics of maternal input in relation to vocabulary development in children learning German -- What happens when adults often use infinitives? -- Frequency mismatches between caregiver input and child language -- Structural versus frequency effects in L1 acquisition of the passive and impersonal in Serbian -- The (non-) effect of input frequency on the acquisition of word order in Norwegian embedded clauses -- Factors determining the acquisition of animacy in Czech -- (Non-)Frequentist perspectives within UG -- A note on acquisition in frequency-based accounts of binding phenomena -- Principles, parameters and probabilities -- Comments -- The role of frequency in language acquisition -- Counting grammars -- List of contributors -- Index