Odynophagia is a medical condition characterized by pain on swallowing due to a disorder of the oesophagus. It's not a countable noun. It has no plural
The word "biopsies" is the plural form of the word. The singular form is "biopsy."
Louse is singular. The plural form is lice.
singular = country plural = countries
The word crisis is singular. The plural form of crisis is crises.
The singular form is it, the plural form is they(subjective) and them (objective).
The plural of oasis is oases.
The word community is singular; the plural form is communities.
The word 'Phenomenon' is singular. The plural form is 'Phenomena'.
The word team is singular; the plural form is teams.
"Agendum" is the singular form of the word. The plural form is "agenda."
The singular form is friend; the plural form is friends.
No, the word "list" is singular. The plural form of "list" is "lists."