If a construction is grammaticalized, its syntagmatic variability decreases. This means that the order freedom of its components shrinks and gets increasingly fixed. As a consequence, when a lexical item is grammaticalized to a formative in a certain construction, it undergoes fixation of its syntagmatic position in this construction. Examples include the following:

The Latin numeral could precede or follow its nominal or even be distanced from it. All of are grammatical and – apart from differences in information structure – synonymous.

This positional freedom was lost in the grammaticalization of the numeral unus to the indefinite article un, for instance in Spanish. Only the order of un esclavo ‘a slave’ is grammatical, which already appears in the example from colloquial Latin.

The relative order of the auxiliary and the non-finite verb in periphrastic constructions is an instructive example. In Classical Latin, this order is relatively free; both orders of are grammatical.

However, the default order at the relevant stage of the language history was for the finite verb to go in clause-final position and, at any rate, to follow a dependent non-finite verb. Thus, it was the order shown by a which entered the course of grammaticalization of the synthetic future. In this course, this order was so totally fixed that the auxiliary became an enclitic on the infinitive.

The development of the periphrastic perfect in the Romance languages used the same verb habere with a dependent non-finite verb form. Here, again, both orders would have been possible in Classical Latin ():

Now the grammaticalization of this construction starts a few centuries later than the grammaticalization of the synthetic future. The default order of a verb and its dependents, including a dependent non-finite verb form, has now changed in the colloquial language. In the construction undergoing grammaticalization, the order gets fixed as the one shown by a. This gives rise to the perfect construction shown in .

Here the auxiliary form of haver ‘have’ precedes the non-finite verb form. It is fixed in this position. However, since the language is not prone to proclisis, it does not coalesce with the full verb as in the earlier case of the synthetic future.