French works as English and the words le prendre are equivalent to take it ( le and it are pronouns ). That means that prendre is not a noun, but a verb. Only some infinitives can be used as nouns : l'aller , le déjeuner, le coucher, le rire, le pouvoir ... , but there is no noun " le prendre". Anyhow the context makes the difference ; for example, savoir can be a verb ( je sais , I know ) or a noun ( un, le savoir , the knowledge ) . So both sentences Il a besoin de le savoir (verb) and Il a besoin du savoir ( noun ) are grammatically correct. The first is quite usual , but the second would need something more to make sense as J'ai besoin du savoir des autres .