Words which are also plurals are?

You're asking about words that are both singular and plural forms! These are called "singularia tantum" (Latin for "singular only"). They can be tricky because they don't follow the usual rules of adding "-s" or "-es" to make them plural.

Here are some examples:

* Sheep: "One sheep" or "many sheep"

* Fish: "One fish" or "many fish"

* Series: "One series" or "multiple series"

* Species: "One species" or "many species"

* Means: "One means" or "several means"

* Data: "One data point" or "a lot of data" (though "datum" is the singular)

Important Note: Some of these words, like "data," are technically plural, even though we use them in singular contexts.

Let me know if you'd like to explore other kinds of interesting words!