"Merci pour votre réactivité," a client wrote to me last week in thanks for a speedy turnaround on a document – and not, as might be assumed, in appreciation of my propensity to react to praise by turning a pleasing shade of pink! Indeed, for English speakers, reactivity describes primarily a chemical property, whereas for French speakers, it is also a desirable character trait.

This week's pair fall into the tricky category of partial false friends. The primary meaning of réactivité/reactivity is the same in both languages: it describes the rate at which a substance undergoes a chemical reaction when mixed with another substance, or the degree to which an organism reacts to a stimulus. Where they differ is in the figurative meaning of the word in French.

In a business context, réactivité describes a company's ability to respond to market demand with the speed of a chemical reaction. Businesses often proclaim it as a core value. Job descriptions list it as a desirable attribute in candidates. There is no single word in English that conveys exactly this combination of speed, initiative, and responsiveness.

As a quality of persons or organisations, réactivité is best translated with a paraphrase, as in the following examples:

• La réactivité de notre département informatique est excellente. // Our IT department's response time is excellent.

• Le Groupe continuera à faire preuve de réactivité en adaptant ses productions à l'évolution de la demande. // The Group will continue to swiftly adapt its products to meet changing demand.

• La part croissante des CDD démontre une réactivité plus rapide de l'emploi aux variations cycliques. // The rising share of short-term contracts indicates that the job market is reacting more quickly to cyclical variations.

When speaking of a person, in a CV for instance, I would be tempted to translate with the adjective proactive; calling someone reactive has a negative connotation in English, suggesting a lack of initiative.

• Votre sens de l'organisation, rigueur et réactivité vous permettront de réussir à ce poste. // To succeed in this role you will need to be highly organised, thorough and proactive.

I admit that the use of proactive here changes the message. However, it may also be symptomatic of cultural differences in work values. Does the ideal employee react quickly to a situation or anticipate it? Answer emails instantly or take time to craft an informed response?

What does réactivité means to you personally or in your industry? Share your thoughts in a comment!