That is the singular form; the plural form is those.
Bacterium is the singular word.
the singular word it is salmon.
singular
Adenoma is the singular of adenomata.
The word 'Phenomenon' is singular. The plural form is 'Phenomena'.
The singular form of the word flagella is flagellum.
singular of the word stitches is stitch.
The word dog is the singular form.
Yes, the word "document" is singular.
The word "hang" is singular.
Lance is singular.
The word "influx" is singular. It refers to the act of flowing in.