 Another category of terms whose singular status raises questions is that of natural kind terms like ‘gold’ and ‘water’. Again, these seem widely to be thought singular at least some of the time. They are frequently counted as rigid. Other related and again apparently singular terms that are sometimes counted rigid include ‘redness’ and ‘loudness’. More controversial are singular terms for properties that are more artificial: ‘bachelorhood’, or ‘soda pop’.   Not just singular terms but also general terms, like ‘tiger’, ‘hot’, and ‘red’ are often recognized as rigid (following Kripke’s suggestion: 1980, p. 134). These terms raise complications not present for singular terms.  I discuss kind and property terms toward the end of this entry.