Old English, like its parent Germanic languages, was a synthetic language, a highly inflected language. Every noun was declined in four cases (in some instances, a fifth "instrumental" case is recorded) and two numbers. In addition, nouns had grammatical gender.
There were two categories of Old English verbs, determined by how they formed their past tense: strong verbs and weak verbs. Strong verbs formed their preterits (past tenses) by ablaut gradation; weak verbs formed their preterits by the addition of a dental suffix, either [t] or [d]. There were seven classes of Old English strong verbs (as there were in the other Germanic Languages), and three classes of weak verbs. In addition, verbs were inflected for person and number (in the subjunctive mood, the only inflection was for number).
Old English pronouns were also more heavily inflected than are their current forms: there were four cases (as there were of nouns), three genders, and three numbers: in addition to singular and plural, there also was a "dual" number, when exactly two were being referred to.
Adjectives were declined much like nouns: two numbers, five cases (again counting the infrequent "instrumental" case), three genders. However, there were two sets of each adjective: weak adjectives and strong adjectives. The weak adjective forms were used in conjunction with demonstratives (this, that, these, those) and possessive pronouns; the strong adjective forms were used in all other cases. The adjective agreed in all ways (number, case, gender) with the noun it modified.
Demonstratives had two numbers, three genders, and four cases. The demonstrative was commonly used to mean simply the article "the." The demonstrative, like the adjective, agreed in all ways with the noun it modified.
In general, Old English syntax was less dependent on word order for meaning, since it was a synthetic language, though word order was beginning to fall into patterns recognizable as modern, i.e., the S-V-O sentence was the norm. Parataxis was common, as the means and the will for subordination were less common in Old English writings.