Differences of "deber" (Spanish) and "devoir" (French)

How do you differenciate "deber" from "devoir"?

Often times I have poeple coming to our center interested in or inquiring about studying two languages at the same time. In most cases it is about learning two languages coming from the same language family, like French and Spanish, Italian and Portuguese, or Norwegian and Swedish.  While it is relatively easy to learn common vocabulary, you have to consider the differences that make those languages unique. 
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For example, as we all know French and Spanish are two romance languages with similar grammar structures and vocabulary.  Let's look at the verbs deber (in Spanish) and devoir (in French). They both come from the same Latin verb debere.  They look similar in form and have similar usage, but the verb deber in Spanish has different nuances.  

​The same verb devoir in French has different translations in Spanish.
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1. Tener que + infinitive (obligation)
For example, the obligation to pay a sum of money:

• El tiene que pagar el médico
• Il doit payer le médicin.   

         (He has to pay the doctor.)

2. Deber+infinitive (an imposed obligation)
For example, an obligation imposed by the law or society or a moral obligation:

• Tu debes trabajar.
• Tu dois travailler.​

          (You must work.)

3. Haber de+infinitive (intention)
For example:

• He de trabajar mañana.
• Je dois travailler demain.

         (I should work tomorrow.)

4. Deber de+infinitive.
For example, a present probability or supposition:

• Ellos deben de estar aquí ahora.
• Ils doivent être ici maintenant.

​         (They should be here by now.)

This is just an example of how languages work. When studying two languages at the same time, you need to go beyond the literal translation and keep in mind the differences and nuances of each language. Not only will  you learn these new languages faster finding many similar words, but also going the extra mile will take you further ahead.