The study investigates the gradual development of morphological specification, as reflected in use of early non-finite verb forms in the speech of three Hebrew-acquiring children (mean age range 1;4–2;2). Children acquiring different languages have been shown to make use of non-finite forms in their initial verb usage. Use of uninflected verbs in matrix clauses has been attributed to the Root or Optional Infinitives phenomenon in generative frameworks, or to the generally stepwise path of acquisition in developmental approaches. Analyses of the longitudinal data presented here suggest that Hebrew-acquiring children do not use infinitival forms before they begin to master inflections productively. Instead, they rely, for several months, on non-affixed “bare stems” as their initial verb forms. Prefix-marked “full” infinitives occur later, typically in well-formed syntactic contexts, alongside productive use of affixed Present-tense (benoni) participial forms. Hebrew-acquiring children thus appear to make selective use of different types of nonfinite forms (initial bare stems followed by Infinitives and benoni), each representing different levels of inflectional knowledge. It is therefore argued here that non-finiteness in early child language is in itself a developmental concept consisting of several sub-phases each of which demonstrates a particular level of linguistic knowledge, motivated by typological features of the ambient language.