Sentence:  In the plural, an &#39;e&#39; is added to the adjective creating the &#39;<WSD>e-form</WSD>,&#39; both for common and neuter gender. (...) An &#39;e&#39; is also added in the definite singular, using "den" and "det" (the), for both genders: ... 
Meaning of the word marked with <WSD> tags:  language The (definite) (singular) and (plural) form of (adjectives), which often end in -e.