Key Difference: A tooth is a small and whitish structure which is found in human mouth. ‘Teeth’ is the plural word for tooth. It falls in the category of irregular plurals. Teeth are used for biting and chewing food.

Tooth refers to a small and whitish structure which is found in mouth of the invertebrates. It is used for chewing food. A tooth is set in the jaws. ‘Teeth’ is just the plural form of tooth. Many times, people tend to think that both words are the same, and thus can be used interchangeably. However, this is absolutely not true.

‘Teeth’ is the plural form of tooth, and therefore teeth should only be used in the collective sense like – Teeth must be brushed properly. Here, in this sentence, one is not referring to a single tooth but all the teeth and therefore teeth word is used.

Tooth is used in a singular form for example - if a doctor asks a patient that which tooth he wants to get removed? Doctor is referring to enquire about a particular tooth. Tooth is also used in idioms like ‘fight tooth and nail’, ‘long in the tooth’ and ‘sweet tooth’.

Teeth present in the front side in men and quadrupeds are called incisors, or incisive or cutting teeth; adjacent to these teeth are the pointed teeth, called canine or dog teeth; and on the sides of the jaws are the molar teeth or grinders. Teeth are composed of calcium, phosphorus, and other minerals. Generally, plural of a singular noun in English is defined by adding  ‘s’ like plural of car is cars. However, ‘teeth’ falls in the category of irregular plurals.

Comparison between Tooth and Teeth:

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