The present article is a follow-up to the paper by Kuz’menko Yu.K. (2017) about the shortening of the long consonants in Danish and in West Germanic languages, in which author tried to show that the long consonants lost their syllable-initial and morpheme-final part (fal-la>falə) in order to provide the coincidence of syllable and morpheme boundaries. The next step in the same direction in the Germanic languages was the shortening of original long stressed vowels (and the change of the contact type free (open) > checked (close). This paper deals with the development of checked contact words in Danish, where the shortening of original long vowels occurs before our very eyes. The vowel shortening and the development of checked and superchecked (stød on consonant) contact in Danish can be observed when comparing three different Danish dictionaries (ODS, DDO and DK) reflecting three stages of this development. The number of sources of checked contact words in Danish is high, because of the Danish consonant shift that shifted almost all the original postvocalic consonants, turning fortis into lenis and lenis into components of diphthongs. Furthermore, the Danish /ð/ has the same shortening effect on the preceding vowel as approximants [w] and [j]. The change of the contact type and vowel shortening also occurred in English (cf. bow, eye and book, dead). The shortening of the original long vowels in Danish and English, which resulted in the increased number of words with the coincidence of syllable and morpheme boundaries is treated in the article as a result of the functioning of a selfadjusting language system which can rebuild itself in accordance with a certain task. In our case this task consists in ensuring a better segmentation of the root morpheme in text (facilitated by the coincidence of the root with the syllable).