When to use reflexive verbs
The previous page looked at the form of French reflexive verbs. We introduced reflexive verbs as being the equivalent of English -self. So for example, se laver means to wash oneself; il se lave means he washes himself.
So as a first approximation, reflexive verbs in French are used where in English the object of the verb is a -self word (myself, yourself, herself, ourselves etc). In these cases, it's usually clear that a reflexive verb is needed, provided you're on your guard for cases where the most usual way of expressing the idea in English might not strictly use a -self word (as mentioned on the previous page, it's much more usual to say he had a shower than he showered himself). However, this isn't actually quite the whole story. In the following sections, we look at some other cases when reflexive verbs are used.
Note that many grammars (and in fact, most grammars written for French speakers) use the term pronominal verbs to refer to what we have so far called reflexive verbs ("pronominal" because they have an extra pronoun inserted). Then, reflexive verbs refer specifically to the usage with the -self meaning.
The exact same form as a reflexive verb can also be used in French with the meaning of each other, one another. So for example, ils s'aiment can be used to mean they love each other (though strictly, if it made sense in the context, it could also still have the reflexive meaning of they love themselves). Similarly, whilst ils se lavent would usually be understood as they get washed, they have a wash, if it made sense in the context, this form could also mean they wash each other.
When used with the each other interpretation, pronominal/reflexive verbs are sometimes called reciprocal verbs.
Usually, it's clear from the choice of verb and from the context which meaning— reflexive or reciprocal— is intended. For example, ils s'écrivent is much more likely to mean they write to each other than they write to themselves (i.e. "each of them writes to himself").
In some cases, a form may be more ambiguous. For example, ils se regardent could a bit more feasibly mean either they look at themselves (i.e. each of them looks at him/herself in the mirror) or they look at one another.
Pronominal ("reflexive") verbs used as a passive
In general, French often uses a pronominal ("reflexive") verb where English uses a passive, especially where the passive expresses a generality, and/or where there is no agent expressed1. For example:
Le fromage se met dans le frigo
Le sushi se mange frais
La société s'est transformée en entreprise internationale
Notice how the first two examples express generalities, or things that are "generally true". In the third example, the meaning is essentially "has been transformed", but the sentence is ambiguous as to whether the company was deliberately transformed, e.g. by some specific effort to enlarge the company, or just by "accidental" growth (more similar to the meaning of become in English). Contrast this with the sentence:
La société a été transformée en entreprise internationale.
The company has been transformed/turned into an international business.
Suggest a change / proposez une modification
where the "true passive" strongly suggests that somebody has performed some deliberate action to grow the company.
Verbs that are reflexive "just because they are"
There are some verbs in French that are reflexive "just because they are". In these cases, more technically called intrinsically pronominal verbs or lexically pronominal verbs, it's difficult to attribute any specific meaning to the pronoun, or say that the verb has a particular meaning without the pronoun.
For example, the verb s'évanouir means to faint. But in reality, the verb is only ever used pronominally (i.e. it's always s'évanouir, and évanouir on its own has no sense). Put another way, if you were to try and paraphrase il s'est évanoui (="he fainted") with an expression of the form he Xed himself, it's not clear what verb/meaning X would actually be. Another example is the expression se souvenir de... meaning to remember...— again, the verb souvenir is never used in French except as a "reflexive" verb2.
1. The agent is the person or thing "performing the action", so in
The postman was bitten by the dog, the dog is the agent.
But it's possible to use the passive without an agent. For example,
if we say Postmen are often bitten, we don't actually express
who or what they're bitten by.