French is a language rich in personal pronouns. As well as the subject pronouns (je/te/il/elle/on/nous/vous/ils/elles), direct object pronouns (me/te/le/la/en/nous/vous/les/on), indirect object pronouns (me/te/lui/y/nous/vous/leur/y) and reflexive pronouns (me/te/se/nous/vous/se) there is also a set of personal pronouns known as disjunctive or stressed pronouns. They are: moi, toi, lui, elle, soi, nous, vous, eux and elles. They are called disjunctive pronouns because they often appear in a section of the sentence that is set apart from the rest. They usually sit at the beginning or the end of the sentence, often separated from the rest by a comma, and they are superfluous in that the sentence would still make sense without their presence. French stressed pronouns are used in other ways besides this purely disjunctive function, but they always carry the impression of superfluity that comes with emphasis.
• Accent tonique emphasis on personal nouns and pronouns
Where English speakers emphasize a word just by pronouncing the word itself in a stressed way (the spoken equivalent of italics or upper case), the French achieve this by tacking on an extra noun or pronoun at the beginning or end of the sentence. This is the ‘accent tonique’, and when a pronoun is used it is a stressed pronoun: ’Toi, tu ne m’as jamais aimée’ or ‘Tu ne m’as jamais aimée, toi’ (YOU never loved me).
• Accent tonique emphasis after c’est and ce sont
Another way in which the French use the ‘accent tonique’ is to insert an essentially superfluous ‘c'est’ or ‘ce sont’ at the beginning of a sentence for emphasis, followed by a stressed pronoun. So, instead of just saying ‘Il m’aime’ (He loves me) it becomes ‘C’est lui qui m’aime’ (He’s the one who loves me).
• Forming and responding to questions without using a verb
Spoken French often utilizes statements followed by a stressed pronoun when validation is sought. It is a form of question, for example: ‘Enfin, on a decidé, et vous?’ (Well, we’ve made a decision, what about you?). A stressed pronoun can also stand alone as the answer to a question: ‘Qui a decidé? Lui.’ (Who made the decision? Him.)
• Stressed pronouns following prepositions
When a personal pronoun follows a preposition such as sans, à, avec, pour and chez, the stressed form of the pronoun is used: ‘Je ne peux pas vivre sans elle’ (I cannot live without her). This also applies when the preposition ‘à’ is used to indicate possession: ‘Cet homme est à moi’ (This man is mine).
• Stressed pronoun + même(s)
Adding a hyphen plus 'même’ to a reflexive pronoun (‘mêmes’ for plural pronouns) adds the extra emphasis that is rendered in English by '–self’ or ‘-selves’: ‘Je l’ai fait moi- même’ (I did it myself).
• Compound subjects and objects in a sentence
Although French has a separate set of subject and direct object pronouns, as soon as the subject becomes compound (e.g. ‘He and I) or the object becomes compound (‘Him and me’), stressed pronouns replace the subject and direct object pronouns. So it is not ‘Tu et il, vous êtes des amants’ but ‘Toi et lui, vous êtes des amants’ (You and he are lovers). The same situation arises with subject groupings in negative expressions using ‘ni..ni..ne’: ‘Ni nous ni eux ne le voulons’ (Neither we nor they want it).
• Stressed pronouns after que when making comparisons
When using ‘que’ to introduce a comparison, if a pronoun follows it is in the stressed form: ‘Elle est plus agée que moi’ (She is older than me). This rule also applies when ‘que’ is used in the negative format ‘ne…que’: ‘Il n’a vu que moi’.
• Seul, aussi, surtout, require stressed pronoun
In French, the introduction of one kind of emphasis usually requires another to accompany it. So words like ‘seul’ (alone), ‘aussi’ (also, as well) and ‘surtout’ (especially), if preceded by a pronoun, will need that pronoun to be the stressed variety: ‘Eux seuls peuvent le faire’ (They alone can do it).
• Exceptions to the rule for verbs requiring indirect object
Verbs usually requiring an indirect object noun (i.e. those verbs normally followed by à + noun) will also require an indirect object pronoun, but some verbs are exceptions to the rule. Instead of having an indirect object pronoun preceding the verb, they are followed by ‘à’ plus the stressed pronoun. Such verbs include ‘être à’ (to belong to), ‘s’intéresser à’ (to be interested in), ‘avoir affaire à’ (to be involved with), ‘penser à’ (to think of), ‘faire attention à’ (to pay attention to) and ‘se fier à’ (to trust in).
To summarize: stressed pronouns are used in French with the ‘accent tonique’, questions and answers without a verb, after prepositions, preceding ‘-même’, in compound subjects and objects, following ‘que’, preceding a specific pair of emphatic adverbs and the adjective ‘seul’, and in place of the indirect object pronoun with certain verbs followed by ‘à’. It’s a fairly long and complicated list but, as usual, after repeated practice the usages will become a habit and sound instinctively correct.