A gerund is essentially a verbal noun. This means the word comes from the stem of a verb, but acts as a noun in the sentence. e.g. "I like reading". In this sentence, 'reading' is the gerund. In latin, gerunds are formed by taking the present stem of the verb and adding -nd- and the neuter singular endings for the second declension. There is o plural gerund. Note: the nominative of the gerund is the infinitive.
e.g. 'legere est difficile' which translates directly as 'to read is difficult' but more commonly as 'reading is difficult'.
acc: legendum reading gen: legendi - of reading dat: legendo - to/for reading abl: legendo - from/with/in/by reading