Language phrase of the day: "Plurale tantum"

While preparing the next linkfest I came across mention that "feces" is only a plural noun.  

A plurale tantum (Latin for 'plural only'; pl. pluralia tantum) is a noun that appears only in the plural form and does not have a singular variant for referring to a single object. 

In English, pluralia tantum are often words that denote objects that occur or function as pairs or sets, such as spectacles, trousers, pants, scissors, clothes, or genitals. Other examples are for collections that, like alms, cannot conceivably be singular. Other examples include suds, jeans, outskirts, odds, riches, gallows (although later treated as singular), surroundings, thanks, and heroics.

In English, a word may have many definitions only some of which are pluralia tantum. The word "glasses" (a set of corrective lenses to improve eyesight) is plurale tantum. In contrast, the word "glass"—either a container for drinks (a count noun) or a vitreous substance (a mass noun)—may be singular or plural. Some words, such as "brain" and "intestine", can be used as either plurale tantum nouns or count nouns.

The term for a noun that appears only in the singular form is singulare tantum (pl.: singularia tantum), such as the English words: information, dust, and wealth.

And while we're at it, see ...

The plural of talisman is talismans

Latin plurals used in the English language

The two spellings’ coexistence – some call it competition – is not unusual: witness appendixes and appendices, formulas and formulae, millenniums and millennia, referendums and referenda, stadiums and stadia, and thesauruses and thesauri, all used regularly...

There are no hard and fast rules about which plural to use and when. In certain cases the Latin is more formal or even affected, but not predictably so. Occasionally the two spellings differentiate in meaning. For example, stigmata normally implies a religious context, while stigmas is the general-purpose plural. Some authorities advise limiting mediums to spiritualists and using media for all other senses of the word, but usage varies.