The R-word er is a phonetically weak form in that it is usually pronounced with a schwa as the nucleus (i.e. /ər/ or /dər/ in certain phonological contexts, e.g. after a vowel or nasal), while the strong R-words have a short or long vowel as the nucleus. Moreover, the weak and strong R-words behave like weak and strong pronouns, respectively. For instance, the examples in (133) show that the weak spatial pro-form erthere behaves like the weak personal subject and object pronouns zeshe and ’mhim in that it cannot be used in coordinated structures, whereas the strong spatial R-words can be used in this context, just like the strong personal pronouns zijshe and hemhim.

The assumption that er is a weak pro-form also accounts for the fact that, as a general rule, it cannot be placed in sentence-initial position; the (a)-examples in (134) show that the normal position of weak object pronouns is right-adjacent to the finite verb in second or the subject in non-topicalized position, and the (b), (c) and (d)-examples show that the same thing holds for the locational pro-form er as well as prepositional and quantitative er.

Weak subject pronouns (with the exception of the weak third person masculine pronoun -iehe) behave markedly differently in this respect; as is shown in (135a), they can either occur in the sentence-initial position or follow the finite verb in second position. Since the expletive er is often assumed to act as a placeholder for the subject position, it is not surprising that it exhibits the same behavior as the weak subject pronouns; note, however, that in this case it is usually pronounced with the short vowel /e/, instead of schwa.

Note that the generalization that non-expletive er cannot occur in sentence-initial position does not hold if er is contained in a larger constituent occupying the sentence-initial position. This is especially the case if the first constituent is a (nominalized) infinitival clause; in (136) we give examples involving the locational pro-form er as well as prepositional and quantitative er.

The examples in (137) show that the weak R-pronoun er also behaves like the weak object pronouns in that it is obligatorily moved into a position preceding clausal adverbials such as waarschijnlijkprobably (unless the movement is blocked by one of the syntactic restrictions discussed in Section 36.3); cf. Van Riemsdijk (1978: ch.5) and Haider et al. (1995).

For the sake of completeness, note that the strong form daar in (137c) can occupy a position within the PP headed by op; this is evidenced by the fact that the complete sequence daar op can be scrambled or be placed in sentence-initial position, as shown in the primed (a)-examples in (138). The primed (b)-examples show that pied piping of the preposition op is not possible in the case of er op; this suggests that er is obligatorily extracted from the PP and moved into some designated position in the middle field of the clause, as in (137b).

The discussion above has shown that the R-word er behaves like a weak pro-form, which must be moved into the position indicated by [+R] in (139); the only exception is the expletive er, which, like weak subject pronouns, can also occupy the first position in the sentence, indicated by XP. The other R-words are more like strong pronouns in that they do not have to move into [+R], i.e. they can remain in their original position and they can also occupy the sentence-initial position XP. We will return to the motivation of this [+R] position in Section 36.5.2.

There are two further remarks that can be made about the position of the R-words. First, note that what holds for the “pure” expletive form er in (140a) also holds for the occurrence of er in (140b), which functions simultaneously as an expletive and as a prepositional R-word. This shows that prepositional er is possible in clause-initial position, as long as it also performs the function of expletive. The (c)-examples show that quantitative er behaves differently in this respect: it can never precede the finite verb in second position. We will return to such cases in Section 36.5.3.

Second, the (a)-examples in (141) show that the obligatory movement of weak object pronouns is clause-bounded; the landing site must be in the same clause as its original position. The remaining examples show that the weak R-word er again behaves in the same way in this respect. From now on, we will use the following abbreviations in the examples to indicate the different syntactic functions of er: expl(etive), loc(ational), quant(itative), and pron(ominal).