I recently came across this sentence:
No tenemos fecha.
which means "We do not have a date." The context of this may be when making an appointment with the dentist and you are saying you do not have an appointment.
But why is "una" avoided, as doesn't one say
No tenemos una fecha
The difference is about generic specification. When you say "No tenemos fecha" fecha is undefined; there are many dates available. But, saying "No tenemos una fecha, the date is no longer generic and is countable. The real intention is to emphasize the fact that there is no date available (of course, we are not really talking about a specific date.) Is the same as saying We don't have **even a single date available**.
Here are several ways you can emphasize:
No tenemos fecha (no emphasis)
No tenemos una fecha (strong emphasis)
Also remember that in Spanish double negation is still a negation.
No tenemos ni una fecha (strong emphasis)
No tenemos ninguna fecha (mild emphasis)
Other examples are
No tenemos naranjas (We are talking about naranjas in a generic sense)
No tenemos una naranja (Although not a specific orange we are emphasizing strongly that we don't even have one)
No tenemos ni una naranja (We are also emphasizing that we don't even have one orange.)
No tenemos ninguna naranja (The most natural way to say it in Spanish; with a mild emphasis.)
In Spanish, the word "un/una" are not usually used to say "we don't have any ...". Actually if you add the "un/una" to the sentence, you should end the sentence with an adjective, for example:
"No tenemos una fecha disponible."
which means "We don't have any available date."
Hope it helps.
I guess this is one of these things where there is no grammatical rule. In this particular case, I understand that fecha is something generic, so it would be like saying We don't have (any) dates. So you don't need to add una, actually it sounds weird if you put it there. A different example could be: No nos queda leche, which means We are out of milk or We don't have (any) milk
A similar case (but slightly different), would be: ¡Ya tenemos casa!, which means We have a flat now!. You don't have to add unaor la. You are referring to "your flat", "the flat", the one that you wanted or needed.
Hope it helps :)
In English, we tend to use the word "a" as an article a lot, just like Spanish uses "the" in the EL o LA forms. If this were to be written with Una, it wouldn't be completely wrong, rather just awkward since it's not as direct as possible. You really only need to use UN o UNA when referring to a quantity. In this case, the message was simple referring to one single thing, making it with out the Una quicker, more to the point and 'better' in terms of using it as a phrase.
