When a relative clause is to serve as an inanimate noun, it is prefixed with "ce": « ce que j'ai dit » ("that which I said", "what I said"). In a prepositional phrase after "ce", the pronoun "lequel" is replaced with the pronoun "quoi": « ce à quoi je pense » ("that about which I am thinking", "what I am thinking about"; note the non-contraction of "ce"), except that "ce dont" is usually preferred to "ce de quoi" ( both meaning "that of which").