The plural of meatus is meatuses or meatus - both forms are accepted.
A meatus is a tubular opening or passage in the body.
The singular form of the demonstrative pronoun 'these' is this.
The singular form of "that" is "it."
No, external auditory meatus and external acoustic meatus refer to the same structure, which is the ear canal that leads from the outer ear to the eardrum.
The singular form of "cuffs" is cuff.
The singular form of binoculars is "binocular."
The singular form of "stratum" is "stratum." The word does not change in its singular form.
The form hypothesis is the singular form. The plural form is hypotheses.
Phenomenon is the singular form of phenomena.
The singular form of "oases" is "oasis."
The singular form of "wash" is "washing."