difference between tener que, hay que and deber
what is the difference between deber, hay que and tener que ?
5 Answers
I would say that there is probably quite a bit of overlap between deber + infinitive and tener que + infinitive. Both can be used to express a certain obligation to do something; however, it is sometimes convenient when analyzing these expressions to think about the differences between the following set of English phrases:
1). I must do something.
2). I ought to do something.
3). I have to do something.
4). I should do something.
Clearly, in certain context each of these can be used relatively interchangeably; however, is is also true that context and usage patterns can also affect whether one of these expressions is used more often than another. The same is often true of these Spanish expressions as well.
Deber + Infinitive:
In many cases, "deber" can be used to give advice:
?Debes perder peso ? You ought to lose weight.
?Debes perder peso gradualmente ? You should lose weight, gradually.
On the other hand, "deber" can also be used to express obligation. Often, the obligation is internally motivated or might have moral implications.
?Debes ser más responsable ? You should/ought to be more responsible.
?Debes ser más paciente ? You should/ought to be more patient.
In this sense it might be helpful to recognize that the word "deber" shares similar origins with English words such as "duty" and "debt" in that each is derived from the Latin word "deb?re" (to owe). Bearing this in mind gives insight into why this expression is so amenable to expressing moral or internally derived obligations.
Debes ser más responsable
? You owe it {to me ~ to yourself ~ to God ~ to your family, etc} to be more responsible.
? You are duty bound to be more responsible.
In my own opinion (and this probably has a lot to do with the particular way that I use English), "deber" is most often translated (at least more naturally) to phrases like "should," "ought to" or "must;" however, I also find it possible to use "have to" in many instances as well. In this regard, I think that when going from Spanish to English, it often becomes a question of usage.
Tener que + Infinitive:
Often "tener que" is used to express obligation similar to "deber;" however, in many cases the obligations are circumstantially motivated or due to some unavoidable necessity. Because "tener que" does not generally entail the same moral or social standards that "deber" does, it would probably sound somewhat less strained to say something like:
Tengo que robar para comer ? I have to steal in order to eat.
rather than:
Debo robar para comer ? I have to (ought to/should/must/its my duty to) steal in order to eat.
The NGLE Manual gives a similar example with:
Las autoridades a veces tienen que cometer actos ilegales ? Sometimes authorities have to commit illegal acts.
vs.
Las autoridades a veces deben cometer actos ilegales ? Sometimes authorities have (a duty) to commit illegal acts!!!???
Another distinction that the NGLE mentions is that when "tener que" is conjugated in the preterit, it is understood that the action has indeed taken place already, so that saying something like:
Tuvo que lavar la ropa pero no la lavó ? He had to wash the clothes but didn't wash them.
sets up a sort of contradiction that is not detected with deber:
Debió lavar la ropa pero no la lavó ? He should have washed the clothes, but he didn't.
Tener que is a personal obligation and hay que is a general obligation e.g. Tengo que limpiar mi habitacción. Para llegar al centro hay que coger el autobús numero 7.
They can all be related to "must"
I must do it - Debo hacerlo
I have to do it - Tengo que hacerlo
Hay que hacerlo - It must be done or one must do it ( I think)
Update:
I have tried to get Bolivians to explain to me the difference between:
Tengo que hacer (algo) - I have to do (something)
Debo hacer (algo) - I must do (something)
but can never get agreement among my students even though I explain that there is a difference in English.
From what I've seen, it seems like the could be ranked from strongest to weakest
1- deber (much like "must" or "have to" in English)
2- tener que (This doesn´t seem to be as strong, but it´s still stronger than "hay que" becuause a specific person or group is usually named.)
3- hay que (This phrase seems to just be saying that it should be done, but it doesn't really name how it will be done or who will do it.)
As you can see however, I have no gramatical reason as to why I think it´s this way, just some limited listening experience.
Hay que - "it is necessary." No one in particular is mentioned.
Tener que - "to have to" The verb conjugation determines who is involved.
Deber - "must, should" More like some type of moral obligation.
