Old English had a highly inflected system of nouns, pronouns, adjectives and verbs. Nouns and adjectives declined based on gender, number and case. Verbs conjugated based on person, number, tense, mood and voice. There were two tenses - present and past. Verbs were either strong, forming the past tense by ablaut, or weak, forming the past tense with dental suffixes. Compound words and derivation through prefixes and suffixes allowed the language to adapt and form new words over time.