159. The Gerund and Supine are used as follows.
a. The Gerund is a verbal noun, corresponding in meaning to the English verbal noun in -ing (§ 502).
loquendī causā for the sake of speaking
Note— The Gerund is found only in the oblique cases. A corresponding nominative is supplied by the Infinitive.
Scrībere est ūtile. Writing (to write) is useful.
ars scrībendī the art of writing
b. The Supine is a noun of the 4th declension (§ 94.b) in form, found only in the accusative ending in -tum, -sum, and the dative or ablative ending in -tū, -sū. The Supine in -um is used after verbs and the Supine in -ū after adjectives (§§ 509 - 510).
Vēnit spectātum. He came to see.
mīrābile dictū wonderful to tell