Some words are the same whether singular of plural. Sheep (oveja) is one such word.
There are others. Here are 8 more:
* Aircraft (but one plane, two planes).
* Deer (ciervo).
* Haddock (merluza).
* Means (in the sense of how something is done or the equipment = manera, medio).
* Trout.
* Series (of a programme on the radio or televisión).
* Shambles (desorden, confusión).
* Offspring (descendencia).
There are others: for another day.
