Essentially there is no difference between a tooth and teeth. The difference is purely in the quantity or the plural spelling of the word.
The plural of tooth is teeth and it is known as an irregular plural.
This irregular plural is like foot and feet when the double ‘oo’ changes to a double ‘ee’.
A native English speaker can hear the difference in the singular and the plural spelling and pronunciation of the word within the context of the sentence and know when the word is correctly used.
A tooth and teeth are the same in structure and anatomical design.
Firstly consider the basic composition of a tooth and or teeth. A tooth is a calcified hard structure that is part of the jaws of many vertebrae. The tooth or teeth are the same in most vertebrates but can be positioned differently. Teeth are not bones but are set in the jaws of the animal and used for chewing and biting. Some animals have one set of teeth while others loose teeth and gain more regularly. Sharks for example grow new teeth every two weeks.
Teeth work together in our mouths and have a collective purpose to chew food, give shape to the mouth and they are important for speech. A single tooth would not be able to achieve this satisfactorily. Children have a set of baby or milk teeth that fall out to make way for the permanent teeth. Dentists have a numbering system for teeth in order to attend to them satisfactorily.
In spite of all the differences discussed and known about teeth or the individual tooth they still remain the same in terms of composition and basic function. A dentist will treat one tooth individually but at the same time assess all the teeth in the patient’s mouth and their function with regard to the bite and patient’s general dental hygiene. It is possible to acquire a false tooth or full set of false teeth.
There are several English idioms using tooth and teeth. ‘Fighting tooth and nail’ is an interesting idiom referring to fighting like an animal fiercely but only referring to one tooth and not to teeth and nails. Then a person who is ‘long in the tooth’ is getting older in years. A narrow escape is made by the ‘skin of your teeth’ however, there is no skin on one’s teeth. A’ sweet tooth’ refers to enjoying sugary things that are not really good for one’s teeth. Teeth are the serrated edge of a saw, and found on a zipper. A fine tooth comb is used for combing delicate hair and has many teeth and if you are looking for ‘hen’s teeth’ then you are bound to be searching for something almost impossible to find.
Dr Seuss, the author of the cheerful grinning Cat in the Hat said:
“Teeth are always in style.”
Therefore it is the collective show of teeth that is attractive. The plural teeth is a group of teeth and each tooth contributes to the million dollar smile.