Gerunds (and gerundives, covered in the next section) are not participles per sē (“by themselves”), but as you will soon see, there is no better place to put them. English does have gerunds, but it doesn't have gerundives. Gerundives are suī generis (“of their own kind”).
Gerunds are verbal nouns. In English they take the form of “-ing” words (e.g., “reading is fundamental”), which makes them identical in appearance to English present participles. Latin gerunds also resemble Latin present participles, but with some important distinctions (like spelling and declension) that will help you recognize and distinguish them without a problem.
The Latin gerund is a second declension neuter noun made from the present stem with the suffix -nd- plus an ending.
Table 15-2 Gerund Declension
Apart from the fact that gerunds have no nominative form, the remaining cases still function with the same uses as they do for any other noun; for example, modus operandī (“way of working”). (If you want a verb to be the subject of another verb, you have to use an infinitive. More on this in Chapter 17.)
Gerunds have a special use. In the accusative preceded by ad, or in the genitive followed by causā or gratiā , they can show purpose much like utnē with the subjunctive “can.”
Vē iī sē gressī sunt ut Romae habitā rent. (They left Veii to live in Rome.)
Vēiī sē gressī sunt ad Romae habitandum.
Vēiī sē gressī sunt Romae habitandī causā.
Vēiī sē gressī sunt Romae habitandī gratiā.
As verbal nouns, gerunds can take objects. When this happens, though, gerundives come into play …
The verb sum, esse, fuī -, futū rus has only one participle: futū rus. It has no gerunds or gerundives either. If you ever find a sentence that is lacking a verb, assume that the missing verb is the appropriate form of sum. For instance, the ablative absolute phrase Caesar duce has no participle but still works: “Since Caesar was the leader …”