Rule 7: Irregular forms

Some words retain the same form, whether singular or plural.

Examples

biceps

facies

scissors

Rule 8: Irregular forms-exception

Decubitus is an adjective, not a noun, and does not have a plural form.

Examples

incorrect: decubiti

correct: decubitus ulcers

not

T: decubiti ulcers

Rule 9: Medical terms derived from Latin or Greek

Words ending in -en; change text ending to -ina

Rule 10: Medical terms derived from Latin or Greek

Words ending in -a; add -e