One of two children born at the same birth is a twin (not, twins).
Two married persons are couple (not, couples).
The two parts between a person’s waist and knees are lap (not, laps).
All of the people from the Yoruba tribe are Yoruba (not Yorubas and this applies to other tribes).
The set of words by which a person is known is the person’s name (not names).
©Dr Garb English Clinic