and ). The situation for the front opening diphthongs is somewhat unclear in some texts. Words written with io in the Heliand, the most extensive record of Old Saxon writing, are often found written variably with ia or even ie in most other texts, notably the later ones. The diphthong eventually merges into in almost every Middle Low German dialect. There also existed 'long' diphthongs , and . These were, however, treated as two-syllable sequences of a long vowel followed by a short one, not proper diphthongs. Grammar Morphology Unlike modern English, Old Saxon was an inflected language rich in morphological diversity. It kept five out of the six distinct cases of Proto-Germanic: the nominative, accusative, genitive, dative and (Vestigially in the oldest texts) instrumental. Old Saxon also had three grammatical numbers (singular, and dual, and plural) and three grammatical genders (masculine, feminine, and neuter). The dual forms occurred in the first and second persons only and referred to groups of exactly two. Nouns Old Saxon nouns were inflected in very different ways following their classes. Here are the endings for dag, "day" an a-stem masculine noun: At the end of the Old Saxon period, distinctions between noun classes began to disappear, and endings from one were often transferred to the other declension, and vice versa. This happened to be a large process, and the most common noun classes started to cause the least represented to disappear. As a result, in Middle Low German, only the former weak n-stem and strong a-stem classes remained. These two noun inflection classes started being added to words not only following the historical belonging of this word, but also following the root of the word. Verbs The Old Saxon verb inflection system reflects an intermediate stage between Old English and Old Dutch, and further Old High German. Unlike Old High German and Old Dutch, but similarly to Old English, it did not preserve the three different verb endings in the plural, all featured as -ad (also -iad or -iod following the different verb inflection classes). Like Old Dutch, it had only two classes of weak verb, with only a few relic verbs of the third weak class (namely four verbs: libbian, seggian, huggian and hebbian). This table sums up all seven Old Saxon strong verb classes and the three weak verb classes: It should be noticed that the third weak verb class includes only