Lexicographers, linguists and grammarians have paid little attention to the study of the French particle sinon . Yet sinon covers a wide range of at least 7 different meanings to which an eighth can be added when sinon is used to introduce a new topic in a conversation. Here we shall make a study of that conversational sinon and show that this particular use of sinon exhibits the same semantic values of the other 7 usages, but expresses involvement on the part of the speaker. Finally, we shall establish that sinon is a fully grammaticalized particle that can be compared with the Dutch anders , which can be used to express an attitude of the speaker. It is not the case of the French autrement and the English otherwise , which are restricted to the expression of semantic contents and textual links.