Using Conjunctions in Spanish: Words that Glue or Unglue a Sentence
What is a Conjunction?
Conjunctions are words that link words, phrases and sentences, like couplings between train cars. They also can be words that unlink or disassociate words in a series..., conjunctions also serve to transition between parts of a discourse.
Let's start with the most basic: and and but (y and pero). When words are linked in a series, the most common and efficient way to mark them as being in a series is to use commas between all of them, until the last pair, when and is inserted between them, instead of a comma. Examples: Tenemos perros, gatos, caballos y otros animales en el zoológico; No hay muchos animales en este zoológico, pero tenemos muchos tipos de monos.
One of the more interesting functions of a word as simple as and (y) is that its use, or omission, can create a rhythm. The abundant use of and (y) is known as polysindeton. The omission of and (y) when it could be used but isn't, is known as asindeton.
Certain conjunctions when used together, such as o ... o and ni ... ni, create correlative constructions. The o ... o combination is equivalent to the English use of either... or and the ni.... ni construction is the equivalent of the English neither .... nor...; the latter being used in sentences that are negative (remember that Spanish requires double negation). For example:
Se me ocurrió entonces que ella o se había salido del edificio o que había tomado el ascensor.
No es ni gato ni liebre.
Finally, observe that when using pero (but), the sentence is affirmative, but when using no, sino (but rather) must be used instead; sino que (but rather) is used when a conjugated verb follows. In other words, sino is used to contradict or correct previous information. For example:
Vamos a la playa, pero primero vamos a comer.
No fue al cine sino al teatro.
No fue al cine sino que se quedó en casa.