definite article
used to indicate a person or thing that has already been mentioned or seen or is clearly understood from the situation
a - used to refer to things or people that are common in daily life
b - used to refer to things that occur in nature
a - used to refer to a particular unit or period of time
b Brit - used to indicate the day on which something happened or will happen
used before the name of a specific person, place, event, work of art, etc.
used to indicate which person or thing you are referring to or discussing
used in titles after a person's name
used before an ordinal number
a - used before a singular noun to refer in a general way to people or things of a particular kind
b - used to indicate the type of musical instrument someone plays
c - used before an adjective that is being used as a noun to refer to all of the people or things that have a particular quality
d - used before a plural noun to indicate that every person or thing of the kind specified is included
e - used before the plural form of a person's last name to indicate that all the members of the family are included
a - used to indicate that a person or thing is the best of its kind
b - used to indicate the most famous person having a particular name;
This sense of the is emphasized in speech.
used to refer in a general way to a specific type of activity
a - used to refer to a part of your body or clothing
b informal - used before a noun that refers to a person's family, job, health, etc.
US