No tenemos ni dedal ni imperdible.

Ni ... ni is the normal Spanish way to say neither ... nor.

So:

• ni dedal ni imperdible = neither a thimble nor a safety pin

It links two items and says that not one and not the other is available.

A very literal structure would be:

• No tenemos ni X ni Y = We don’t have either X or Y / We have neither X nor Y

Yes, from an English point of view it looks like a double negative, but in Spanish this is completely normal. Spanish uses negative concord, which means multiple negative words often appear together in the same sentence.

So:

• No tenemos ni dedal ni imperdible

is standard Spanish, not incorrect or extra-negative.

English usually avoids this in standard grammar, but Spanish does not. In fact, with this structure, no is required because the negative phrase comes after the verb.

Because the negative elements ni dedal ni imperdible come after the verb.

In Spanish, if the negative word or phrase comes after the verb, you normally keep no before the verb:

• No tenemos ni dedal ni imperdible.

Compare that with cases where a negative word comes before the verb:

• Nadie vino. = Nobody came.
• Nunca comemos eso. = We never eat that.

There, Spanish does not add no before the verb.

But with ni ... ni after the verb, no stays:

• No tenemos ni esto ni aquello.

Because Spanish normally repeats ni before each item in this paired structure:

• ni X ni Y

So:

• ni dedal ni imperdible

This is the standard pattern, just like English neither X nor Y.

Repeating it makes the pairing clear and natural.

In Spanish, when talking about unspecified things in a general way—especially in negative sentences—articles are often omitted.

So:

• No tenemos ni dedal ni imperdible

sounds natural as We don’t have a thimble or a safety pin / We have neither thimble nor safety pin in a general sense.

You could also hear:

• No tenemos ni un dedal ni un imperdible.

That version is also correct, but it can sound a bit more emphatic, as if stressing not even one of either item.

So both are possible, but the version without articles is very normal.

Because Spanish often leaves out subject pronouns when the verb form already shows who the subject is.

• tenemos = we have

The ending -emos tells you the subject is we.

So:

• No tenemos ni dedal ni imperdible.

already means We don’t have neither a thimble nor a safety pin without needing nosotros.

You could say:

• Nosotros no tenemos ni dedal ni imperdible

but that would usually add emphasis or contrast, such as we don’t have them, though someone else might.

Tenemos is the 1st person plural present indicative form of tener.

• tener = to have
• tenemos = we have

So the sentence is in the present tense:

• No tenemos ni dedal ni imperdible.
• We don’t have either a thimble or a safety pin.

Yes, both are masculine singular nouns:

• el dedal
• el imperdible

That is why, if you included an indefinite article, it would be:

• un dedal
• un imperdible

Learners will sometimes try that, but the most natural and standard structure here is:

• No tenemos ni dedal ni imperdible

Using ni before both elements clearly creates the neither/nor pattern.

Without the first ni, the sentence sounds less balanced and is not the usual way to express this idea.

So for this meaning, it is best to learn:

• no + verb + ni X ni Y

It can match either of those English versions depending on how you translate it.

Spanish:

• No tenemos ni dedal ni imperdible.

Natural English equivalents:

• We have neither a thimble nor a safety pin.
• We don’t have either a thimble or a safety pin.

Both communicate the same basic idea. Spanish simply uses its own negative structure with no and ni ... ni.

Yes. Ni is a very common negative connector in Spanish. Besides ni ... ni, you can also see it in other patterns, for example:

• No come ni bebe. = He neither eats nor drinks.
• No llama ni escribe. = She neither calls nor writes.

So the sentence you were given follows a very common Spanish pattern:

• No + verb + ni + item/action + ni + item/action